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RFC3060 - Policy Core Information Model -- Version 1 Specification

王朝other·作者佚名  2008-05-31
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Network Working Group B. Moore

Request for Comments: 3060 IBM

Category: Standards Track E. Ellesson

LongBoard, Inc.

J. Strassner

A. Westerinen

Cisco Systems

February 2001

Policy Core Information Model -- Version 1 Specification

Status of this Memo

This document specifies an Internet standards track protocol for the

Internet community, and requests discussion and suggestions for

improvements. Please refer to the current edition of the "Internet

Official Protocol Standards" (STD 1) for the standardization state

and status of this protocol. Distribution of this memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (2001). All Rights Reserved.

Abstract

This document presents the object-oriented information model for

representing policy information developed jointly in the IETF Policy

Framework WG and as extensions to the Common Information Model (CIM)

activity in the Distributed Management Task Force (DMTF). This model

defines two hierarchies of object classes: strUCtural classes

representing policy information and control of policies, and

association classes that indicate how instances of the structural

classes are related to each other. Subsequent documents will define

mappings of this information model to various concrete

implementations, for example, to a Directory that uses LDAPv3 as its

Access protocol.

Table of Contents

1. Introduction.................................................... 4

2. Modeling Policies............................................... 5

2.1. Policy Scope............................................... 8

2.2. Declarative versus Procedural Model........................ 8

3. Overview of the Policy Core Information Model.................. 10

4. Inheritance Hierarchies for the Policy Core Information Model.. 13

4.1. Implications of CIM Inheritance........................... 15

5. Details of the Model........................................... 15

5.1. Reusable versus Rule-Specific Conditions and Actions...... 15

5.2. Roles..................................................... 17

5.2.1. Roles and Role Combinations............................. 17

5.2.2. The PolicyRoles Property................................ 21

5.3. Local Time and UTC Time in PolicyTimePeriodConditions..... 21

5.4. CIM Data Types............................................ 23

5.5. Comparison between CIM and LDAP Class Specifications...... 24

6. Class Definitions.............................................. 25

6.1. The Abstract Class "Policy"............................... 25

6.1.1. The Property "CommonName (CN)".......................... 26

6.1.2. The Multi-valued Property "PolicyKeyWords".............. 26

6.1.3. The Property "Caption" (Inherited from ManagedElement).. 27

6.1.4. The Property "Description" (Inherited from

ManagedElement)......................................... 27

6.2. The Class "PolicyGroup"................................... 27

6.3. The Class "PolicyRule".................................... 29

6.3.1. The Property "Enabled".................................. 31

6.3.2. The Property "ConditionListType"........................ 31

6.3.3. The Property "RuleUsage"................................ 31

6.3.4. The Property "Priority"................................. 32

6.3.5. The Property "Mandatory"................................ 32

6.3.6. The Property "SequencedActions"......................... 33

6.3.7. The Multi-valued Property "PolicyRoles"................. 33

6.4. The Abstract Class "PolicyCondition"...................... 34

6.5. The Class "PolicyTimePeriodCondition"..................... 36

6.5.1. The Property "TimePeriod"............................... 38

6.5.2. The Property "MonthOfYearMask".......................... 39

6.5.3. The Property "DayOfMonthMask"........................... 39

6.5.4. The Property "DayOfWeekMask"............................ 40

6.5.5. The Property "TimeOfDayMask"............................ 41

6.5.6. The Property "LocalOrUtcTime"........................... 42

6.6. The Class "VendorPolicyCondition"......................... 42

6.6.1. The Multi-valued Property "Constraint".................. 43

6.6.2. The Property "ConstraintEncoding"....................... 43

6.7. The Abstract Class "PolicyAction"......................... 44

6.8. The Class "VendorPolicyAction"............................ 45

6.8.1. The Multi-valued Property "ActionData".................. 45

6.8.2. The Property "ActionEncoding"........................... 46

6.9. The Class "PolicyRepository".............................. 46

7. Association and Aggregation Definitions........................ 46

7.1. Associations.............................................. 47

7.2. Aggregations.............................................. 47

7.3. The Abstract Aggregation "PolicyComponent................. 47

7.4. The Aggregation "PolicyGroupInPolicyGroup"................ 47

7.4.1. The Reference "GroupComponent".......................... 48

7.4.2. The Reference "PartComponent"........................... 48

7.5. The Aggregation "PolicyRuleInPolicyGroup"................. 48

7.5.1. The Reference "GroupComponent".......................... 49

7.5.2. The Reference "PartComponent"........................... 49

7.6. The Aggregation "PolicyConditionInPolicyRule"............. 49

7.6.1. The Reference "GroupComponent".......................... 50

7.6.2. The Reference "PartComponent"........................... 50

7.6.3. The Property "GroupNumber".............................. 50

7.6.4. The Property "ConditionNegated"......................... 51

7.7. The Aggregation "PolicyRuleValidityPeriod"................ 51

7.7.1. The Reference "GroupComponent".......................... 52

7.7.2. The Reference "PartComponent"........................... 52

7.8. The Aggregation "PolicyActionInPolicyRule"................ 52

7.8.1. The Reference "GroupComponent".......................... 53

7.8.2. The Reference "PartComponent"........................... 53

7.8.3. The Property "ActionOrder".............................. 53

7.9. The Abstract Association "PolicyInSystem"................. 54

7.10. The Weak Association "PolicyGroupInSystem"............... 55

7.10.1. The Reference "Antecedent"............................. 55

7.10.2. The Reference "Dependent".............................. 55

7.11. The Weak Association "PolicyRuleInSystem"................ 56

7.11.1. The Reference "Antecedent"............................. 56

7.11.2. The Reference "Dependent".............................. 56

7.12. The Association "PolicyConditionInPolicyRepository"...... 56

7.12.1. The Reference "Antecedent"............................. 57

7.12.2. The Reference "Dependent".............................. 57

7.13. The Association "PolicyActionInPolicyRepository"......... 57

7.13.1. The Reference "Antecedent"............................. 58

7.13.2. The Reference "Dependent".............................. 58

7.14. The Aggregation "PolicyRepositoryInPolicyRepository"..... 58

7.14.1. The Reference "GroupComponent"......................... 58

7.14.2. The Reference "PartComponent".......................... 59

8. Intellectual Property.......................................... 59

9. Acknowledgements............................................... 59

10. Security Considerations....................................... 60

11. References.................................................... 62

12. Authors' Addresses............................................ 64

13. Appendix A: Class Identification in a Native CIM

Implementation................................................ 65

13.1. Naming Instances of PolicyGroup and PolicyRule........... 65

13.1.1. PolicyGroup's CIM Keys................................. 65

13.1.2. PolicyRule's CIM Keys.................................. 66

13.2. Naming Instances of PolicyCondition and Its Subclasses... 67

13.2.1. PolicyCondition's CIM Keys............................. 69

13.3. Naming Instances of PolicyAction and Its Subclasses...... 71

13.4. Naming Instances of PolicyRepository..................... 72

13.5. Role of the CreationClassName Property in Naming......... 73

13.6. Object References........................................ 73

14. Appendix B: The Core Policy MOF.............................. 75

15. Full Copyright Statement..................................... 100

1. Introduction

This document presents the object-oriented information model for

representing policy information currently under joint development in

the IETF Policy Framework WG and as extensions to the Common

Information Model (CIM) activity in the Distributed Management Task

Force (DMTF). This model defines two hierarchies of object classes:

structural classes representing policy information and control of

policies, and association classes that indicate how instances of the

structural classes are related to each other. Subsequent documents

will define mappings of this information model to various concrete

implementations, for example, to a directory that uses LDAPv3 as its

access protocol. The components of the CIM schema are available via

the following URL: http://www.dmtf.org/spec/cims.Html [1].

The policy classes and associations defined in this model are

sufficiently generic to allow them to represent policies related to

anything. However, it is eXPected that their initial application in

the IETF will be for representing policies related to QoS (DiffServ

and IntServ) and to IPSec. Policy models for application-specific

areas such as these may extend the Core Model in several ways. The

preferred way is to use the PolicyGroup, PolicyRule, and

PolicyTimePeriodCondition classes directly, as a foundation for

representing and communicating policy information. Then, specific

subclasses derived from PolicyCondition and PolicyAction can capture

application-specific definitions of conditions and actions of

policies.

Two subclasses, VendorPolicyCondition and VendorPolicyAction, are

also included in this document, to provide a standard extension

mechanism for vendor-specific extensions to the Policy Core

Information Model.

This document fits into the overall framework for representing,

deploying, and managing policies being developed by the Policy

Framework Working Group. It traces its origins to work that was

originally done for the Directory-enabled Networks (DEN)

specification, reference [5]. Work on the DEN specification by the

DEN Ad-Hoc Working Group itself has been completed. Further work to

standardize the models contained in it will be the responsibility of

selected working groups of the CIM effort in the Distributed

Management Task Force (DMTF). DMTF standardization of the core

policy model is the responsibility of the SLA Policy working group in

the DMTF.

This document is organized in the following manner:

o Section 2 provides a general overview of policies and how they are

modeled.

o Section 3 presents a high-level overview of the classes and

associations comprising the Policy Core Information Model.

o The remainder of the document presents the detailed specifications

for each of the classes and associations.

o Appendix A overviews naming for native CIM implementations. Other

mappings, such as LDAPv3, will have their own naming mechanisms.

o Appendix B reproduces the DMTF's Core Policy MOF specification.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",

"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this

document are to be interpreted as described in RFC2119, reference

[3].

2. Modeling Policies

The classes comprising the Policy Core Information Model are intended

to serve as an extensible class hierarchy (through specialization)

for defining policy objects that enable application developers,

network administrators, and policy administrators to represent

policies of different types.

One way to think of a policy-controlled network is to first model the

network as a state machine and then use policy to control which state

a policy-controlled device should be in or is allowed to be in at any

given time. Given this approach, policy is applied using a set of

policy rules. Each policy rule consists of a set of conditions and a

set of actions. Policy rules may be aggregated into policy groups.

These groups may be nested, to represent a hierarchy of policies.

The set of conditions associated with a policy rule specifies when

the policy rule is applicable. The set of conditions can be

expressed as either an ORed set of ANDed sets of condition statements

or an ANDed set of ORed sets of statements. Individual condition

statements can also be negated. These combinations are termed,

respectively, Disjunctive Normal Form (DNF) and Conjunctive Normal

Form (CNF) for the conditions.

If the set of conditions associated with a policy rule evaluates to

TRUE, then a set of actions that either maintain the current state of

the object or transition the object to a new state may be executed.

For the set of actions associated with a policy rule, it is possible

to specify an order of execution, as well as an indication of whether

the order is required or merely recommended. It is also possible to

indicate that the order in which the actions are executed does not

matter.

Policy rules themselves can be prioritized. One common reason for

doing this is to express an overall policy that has a general case

with a few specific exceptions.

For example, a general QoS policy rule might specify that traffic

originating from members of the engineering group is to get Bronze

Service. A second policy rule might express an exception: traffic

originating from John, a specific member of the engineering group, is

to get Gold Service. Since traffic originating from John satisfies

the conditions of both policy rules, and since the actions associated

with the two rules are incompatible, a priority needs to be

established. By giving the second rule (the exception) a higher

priority than the first rule (the general case), a policy

administrator can get the desired effect: traffic originating from

John gets Gold Service, and traffic originating from all the other

members of the engineering group gets Bronze Service.

Policies can either be used in a stand-alone fashion or aggregated

into policy groups to perform more elaborate functions. Stand-alone

policies are called policy rules. Policy groups are aggregations of

policy rules, or aggregations of policy groups, but not both. Policy

groups can model intricate interactions between objects that have

complex interdependencies. Examples of this include a sophisticated

user logon policy that sets up application access, security, and

reconfigures network connections based on a combination of user

identity, network location, logon method and time of day. A policy

group represents a unit of reusability and manageability in that its

management is handled by an identifiable group of administrators and

its policy rules would be consistently applied

Stand-alone policies are those that can be expressed in a simple

statement. They can be represented effectively in schemata or MIBs.

Examples of this are VLAN assignments, simple YES/NO QoS requests,

and IP address allocations. A specific design goal of this model is

to support both stand-alone and aggregated policies.

Policy groups and rules can be classified by their purpose and

intent. This classification is useful in querying or grouping policy

rules. It indicates whether the policy is used to motivate when or

how an action occurs, or to characterize services (that can then be

used, for example, to bind clients to network services). Describing

each of these concepts in more detail,

o Motivational Policies are solely targeted at whether or how a

policy's goal is accomplished. Configuration and Usage Policies

are specific kinds of Motivational Policies. Another example is

the scheduling of file backup based on disk write activity from

8am to 3pm, M-F.

o Configuration Policies define the default (or generic) setup of a

managed entity (for example, a network service). Examples of

Configuration Policies are the setup of a network forwarding

service or a network-hosted print queue.

o Installation Policies define what can and cannot be put on a

system or component, as well as the configuration of the

mechanisms that perform the install. Installation policies

typically represent specific administrative permissions, and can

also represent dependencies between different components (e.g., to

complete the installation of component A, components B and C must

be previously successfully installed or uninstalled).

o Error and Event Policies. For example, if a device fails between

8am and 9pm, call the system administrator, otherwise call the

Help Desk.

o Usage Policies control the selection and configuration of entities

based on specific "usage" data. Configuration Policies can be

modified or simply re-applied by Usage Policies. Examples of

Usage Policies include upgrading network forwarding services after

a user is verified to be a member of a "gold" service group, or

reconfiguring a printer to be able to handle the next job in its

queue.

o Security Policies deal with verifying that the client is actually

who the client purports to be, permitting or denying access to

resources, selecting and applying appropriate authentication

mechanisms, and performing accounting and auditing of resources.

o Service Policies characterize network and other services (not use

them). For example, all wide-area backbone interfaces shall use a

specific type of queuing.

Service policies describe services available in the network.

Usage policies describe the particular binding of a client of the

network to services available in the network.

These categories are represented in the Policy Core Information Model

by special values defined for the PolicyKeywords property of the

abstract class Policy.

2.1. Policy Scope

Policies represent business goals and objectives. A translation must

be made between these goals and objectives and their realization in

the network. An example of this could be a Service Level Agreement

(SLA), and its objectives and metrics (Service Level Objectives, or

SLOs), that are used to specify services that the network will

provide for a given client. The SLA will usually be written in

high-level business terminology. SLOs address more specific metrics

in support of the SLA. These high-level descriptions of network

services and metrics must be translated into lower-level, but also

vendor-and device-independent specifications. The Policy Core

Information Model classes are intended to serve as the foundation for

these lower-level, vendor- and device-independent specifications.

It is envisioned that the definition of the Policy Core Informational

Model in this document is generic in nature and is applicable to

Quality of Service (QoS), to non-QoS networking applications (e.g.,

DHCP and IPSec), and to non-networking applications (e.g., backup

policies, auditing access, etc.).

2.2. Declarative versus Procedural Model

The design of the Policy Core Information Model is influenced by a

declarative, not procedural, approach. More formally, a declarative

language is used to describe relational and functional languages.

Declarative languages describe relationships between variables in

terms of functions or inference rules, to which the interpreter or

compiler can apply a fixed algorithm in order to produce a result.

An imperative (or procedural) language specifies an explicit sequence

of steps to follow in order to produce a result.

It is important to note that this information model does not rule out

the use of procedural languages. Rather, it recognizes that both

declarative as well as procedural languages can be used to implement

policy. This information model is better viewed as being declarative

because the sequence of steps for doing the processing of declarative

statements tends to be left to the implementer. However, we have

provided the option of expressing the desired order of action

execution in this policy information model, and for expressing

whether the order is mandatory or not. In addition, rather than

trying to define algorithms or sets of instructions or steps that

must be followed by a policy rule, we instead define a set of modular

building blocks and relationships that can be used in a declarative

or procedural fashion to define policies.

Compare this to a strictly procedural model. Taking such an approach

would require that we specify the condition testing sequence, and the

action execution sequence, in the policy repository itself. This

would, indeed, constrain the implementer. This is why the policy

model is characterized as a declarative one. That is, the

information model defines a set of attributes, and a set of entities

that contain these attributes. However, it does NOT define either

the algorithm to produce a result using the attributes or an explicit

sequence of steps to produce a result.

There are several design considerations and trade-offs to make in

this respect.

1. On the one hand, we would like a policy definition language to be

reasonably human-friendly for ease of definitions and diagnostics.

On the other hand, given the diversity of devices (in terms of

their processing capabilities) which could act as policy decision

points, we would like to keep the language somewhat machine-

friendly. That is, it should be relatively simple to automate the

parsing and processing of the language in network elements. The

approach taken is to provide a set of classes and attributes that

can be combined in either a declarative or procedural approach to

express policies that manage network elements and services. The

key point is to avoid trying to standardize rules or sets of steps

to be followed in defining a policy. These must be left up to an

implementation. Interoperability is achieved by standardizing the

building blocks that are used to represent policy data and

information.

2. An important decision to make is the semantic style of the

representation of the information.

The declarative approach that we are describing falls short of

being a "true" declarative model. Such a model would also specify

the algorithms used to combine the information and policy rules to

achieve particular behavior. We avoid specifying algorithms for

the same reason that we avoid specifying sets of steps to be

followed in a policy rule. However, the design of the information

model more closely follows that of a declarative language, and may

be easier to understand if such a conceptual model is used. This

leads to our third point, acknowledging a lack of "completeness"

and instead relying on presenting information that the policy

processing entity will work with.

3. It is important to control the complexity of the specification,

trading off richness of expression of data in the core information

model for ease of implementation and use. It is important to

acknowledge the collective lack of experience in the field

regarding policies to control and manage network services and

hence avoid the temptation of aiming for "completeness". We

should instead strive to facilitate definition of a set of common

policies that customers require today (e.g., VPN and QoS) and

allow migration paths towards supporting complex policies as

customer needs and our understanding of these policies evolve with

experience. Specifically, in the context of the declarative style

language discussed above, it is important to avoid having full

blown predicate calculus as the language, as it would render many

important problems such as consistency checking and policy

decision point algorithms intractable. It is useful to consider a

reasonably constrained language from these perspectives.

The Policy Core Information Model strikes a balance between

complexity and lack of power by using the well understood logical

concepts of Disjunctive Normal Form and Conjunctive Normal Form for

combining simple policy conditions into more complex ones.

3. Overview of the Policy Core Information Model

The following diagram provides an overview of the five central

classes comprising the Policy Core Information Model, their

associations to each other, and their associations to other classes

in the overall CIM model. Note that the abstract class Policy and

the two extension classes VendorPolicyCondition and

VendorPolicyAction are not shown.

NOTE: For cardinalities, "*" is an abbreviation for "0..n".

+-----------+

System

..... +--^-----^--+ .....

. . 1. 1. . .

*.(a).* .(b) .(c) *.(d).*

+--v---v---------+ . . +-v---v------------+

PolicyGroup <........ . PolicyRepository

w * .

+------^---------+ . +-----^---------^--+

*. . 0..1 . 0..1 .

.(e) . .(f) .(g)

*. . . .

+------v------+ w * . . .

<................. . .

PolicyRule . .

. .

. .

<........................ . .

* (h) . . .

. . .

. . .

. . .

. . .

. . .

. . .

.* .* .

+---------v-------v--+ .

PolicyCondition .

*+--------------------+ .

(i) ^ .

<.............. I .

* . I .

.* ^ .

+----v----------------------+ .

PolicyTimePeriodCondition .

+---------------------------+ .

(j) .

<......................... .

* . .

.* .

+----------v---------+* .

PolicyAction <.......

+-------------+ +--------------------+

Figure 1. Overview of the Core Policy Classes and Relationships

In this figure the boxes represent the classes, and the dotted arrows

represent the associations. The following associations appear:

(a) PolicyGroupInPolicyGroup

(b) PolicyGroupInSystem

(c) PolicyRuleInSystem

(d) PolicyRepositoryInPolicyRepository

(e) PolicyRuleInPolicyGroup

(f) PolicyConditionInPolicyRepository

(g) PolicyActionInPolicyRepository

(h) PolicyConditionInPolicyRule

(i) PolicyRuleValidityPeriod

(j) PolicyActionInPolicyRule

An association always connects two classes. The "two" classes may,

however, be the same class, as is the case with the

PolicyGroupInPolicyGroup association, which represents the recursive

containment of PolicyGroups in other PolicyGroups. The

PolicyRepositoryInPolicyRepository association is recursive in the

same way.

An association includes cardinalities for each of the related

classes. These cardinalities indicate how many instances of each

class may be related to an instance of the other class. For example,

the PolicyRuleInPolicyGroup association has the cardinality range "*'

(that is, "0..n") for both the PolicyGroup and PolicyRule classes.

These ranges are interpreted as follows:

o The "*" written next to PolicyGroup indicates that a PolicyRule

may be related to no PolicyGroups, to one PolicyGroup, or to more

than one PolicyGroup via the PolicyRuleInPolicyGroup association.

In other words, a PolicyRule may be contained in no PolicyGroups,

in one PolicyGroups, or in more than one PolicyGroup.

o The "*" written next to PolicyRule indicates that a PolicyGroup

may be related to no PolicyRules, to one PolicyRule, or to more

than one PolicyRule via the PolicyRuleInPolicyGroup association.

In other words, a PolicyGroup may contain no PolicyRules, one

PolicyRule, or more than one PolicyRule.

The "w" written next to the PolicyGroupInSystem and

PolicyRuleInSystem indicates that these are what CIM terms

"aggregations with weak references", or more briefly, "weak

aggregations". A weak aggregation is simply an indication of a

naming scope. Thus these two aggregations indicate that an instance

of a PolicyGroup or PolicyRule is named within the scope of a System

object. A weak aggregation implicitly has the cardinality 1..1 at

the end opposite the 'w'.

The associations shown in Figure 1 are discussed in more detail in

Section 7.

4. Inheritance Hierarchies for the Policy Core Information Model

The following diagram illustrates the inheritance hierarchy for the

core policy classes:

ManagedElement (abstract)

+--Policy (abstract)

+---PolicyGroup

+---PolicyRule

+---PolicyCondition (abstract)

+---PolicyTimePeriodCondition

+---VendorPolicyCondition

+---PolicyAction (abstract)

+---VendorPolicyAction

+--ManagedSystemElement (abstract)

+--LogicalElement (abstract)

+--System (abstract)

+--AdminDomain (abstract)

+---PolicyRepository

Figure 2. Inheritance Hierarchy for the Core Policy Classes

ManagedElement, ManagedSystemElement, LogicalElement, System, and

AdminDomain are defined in the CIM schema [1]. These classes are not

discussed in detail in this document.

In CIM, associations are also modeled as classes. For the Policy

Core Information Model, the inheritance hierarchy for the

associations is as follows:

[unrooted]

+---PolicyComponent (abstract)

+---PolicyGroupInPolicyGroup

+---PolicyRuleInPolicyGroup

+---PolicyConditionInPolicyRule

+---PolicyRuleValidityPeriod

+---PolicyActionInPolicyRule

+---Dependency (abstract)

+---PolicyInSystem (abstract)

+---PolicyGroupInSystem

+---PolicyRuleInSystem

+---PolicyConditionInPolicyRepository

+---PolicyActionInPolicyRepository

+---Component (abstract)

+---SystemComponent

+---PolicyRepositoryInPolicyRepository

Figure 3. Inheritance Hierarchy for the Core Policy Associations

The Dependency, Component, and SystemComponent associations are

defined in the CIM schema [1], and are not discussed further in this

document.

4.1. Implications of CIM Inheritance

From the CIM schema, both properties and associations are inherited

to the Policy classes. For example, the class ManagedElement is

referenced in the associations Dependency, Statistics and

MemberOfCollection. And, the Dependency association is in turn

referenced in the DependencyContext association. At this very

abstract and high level in the inheritance hierarchy, the number of

these associations is very small and their semantics are quite

general.

Many of these inherited associations convey additional semantics that

are not needed in understanding the Policy Core Information Model.

In fact, they are defined as OPTIONAL in the CIM Schema - since their

cardinality is "0..n" on all references. The PCIM document

specifically discusses what is necessary to support and instantiate.

For example, through subclassing of the Dependency association, the

exact Dependency semantics in PCIM are described.

So, one may wonder what to do with these other inherited

associations. The answer is "ignore them unless you need them". You

would need them to describe additional information and semantics for

policy data. For example, it may be necessary to capture statistical

data for a PolicyRule (either for the rule in a repository or for

when it is executing in a policy system). Some examples of

statistical data for a rule are the number of times it was

downloaded, the number of times its conditions were evaluated, and

the number of times its actions were executed. (These types of data

would be described in a subclass of CIM_StatisticalInformation.) In

these cases, the Statistics association inherited from ManagedElement

to PolicyRule may be used to describe the tie between an instance of

a PolicyRule and the set of statistics for it.

5. Details of the Model

The following subsections discuss several specific issues related to

the Policy Core Information Model.

5.1. Reusable versus Rule-Specific Conditions and Actions

Policy conditions and policy actions can be partitioned into two

groups: ones associated with a single policy rule, and ones that are

reusable, in the sense that they may be associated with more than one

policy rule. Conditions and actions in the first group are termed

"rule-specific" conditions and actions; those in the second group are

characterized as "reusable".

It is important to understand that the difference between a rule-

specific condition or action and a reusable one is based on the

intent of the policy administrator for the condition or action,

rather than on the current associations in which the condition or

action participates. Thus a reusable condition or action (that is,

one that a policy administrator has created to be reusable) may at

some point in time be associated with exactly one policy rule,

without thereby becoming rule-specific.

There is no inherent difference between a rule-specific condition or

action and a reusable one. There are, however, differences in how

they are treated in a policy repository. For example, it's natural

to make the access permissions for a rule-specific condition or

action identical to those for the rule itself. It's also natural for

a rule-specific condition or action to be removed from the policy

repository at the same time the rule is. With reusable conditions

and actions, on the other hand, access permissions and existence

criteria must be expressible without reference to a policy rule.

The preceding paragraph does not contain an exhaustive list of the

ways in which reusable and rule-specific conditions should be treated

differently. Its purpose is merely to justify making a semantic

distinction between rule-specific and reusable, and then reflecting

this distinction in the policy model itself.

An issue is highlighted by reusable and rule-specific policy

conditions and policy actions: the lack of a programmatic capability

for expressing complex constraints involving multiple associations.

Taking PolicyCondition as an example, there are two aggregations to

look at. PolicyConditionInPolicyRule has the cardinality * at both

ends, and PolicyConditionInPolicyRepository has the cardinality * at

the PolicyCondition end, and [0..1] at the PolicyRepository end.

Globally, these cardinalities are correct. However, there's more to

the story, which only becomes clear if we examine the cardinalities

separately for the two cases of a rule-specific PolicyCondition and a

reusable one.

For a rule-specific PolicyCondition, the cardinality of

PolicyConditionInPolicyRule at the PolicyRule end is [1..1], rather

than [0..n] (recall that * is an abbreviation for [0..n]), since the

condition is unique to one policy rule. And the cardinality of

PolicyConditionInPolicyRepository at the PolicyRepository end is

[0..0], since the condition is not in the "re-usable" repository.

This is OK, since these are both subsets of the specified

cardinalities.

For a reusable PolicyCondition, however, the cardinality of

PolicyConditionInPolicyRepository at the PolicyRepository end is

[1..1], since the condition must be in the repository. And, the

cardinality of PolicyConditionInPolicyRule at the PolicyRule end is

[0..n]. This last point is important: a reusable PolicyCondition

may be associated with 0, 1, or more than 1 PolicyRules, via exactly

the same association PolicyConditionInPolicyRule that binds a rule-

specific condition to its PolicyRule.

Currently the only way to document constraints of this type is

textually. More formal methods for documenting complex constraints

are needed.

5.2. Roles

5.2.1. Roles and Role Combinations

The concept of role is central to the design of the entire Policy

Framework. The idea behind roles is a simple one. Rather than

configuring, and then later having to update the configuration of,

hundreds or thousands (or more) of resources in a network, a policy

administrator assigns each resource to one or more roles, and then

specifies the policies for each of these roles. The Policy Framework

is then responsible for configuring each of the resources associated

with a role in such a way that it behaves according to the policies

specified for that role. When network behavior must be changed, the

policy administrator can perform a single update to the policy for a

role, and the Policy Framework will ensure that the necessary

configuration updates are performed on all the resources playing that

role.

A more formal definition of a role is as follows:

A role is a type of attribute that is used to select one or more

policies for a set of entities and/or components from among a much

larger set of available policies.

Roles can be combined together. Here is a formal definition of a

"role- combination":

A role-combination is a set of attributes that are used to select

one or more policies for a set of entities and/or components from

among a much larger set of available policies. As the examples

below illustrate, the selection process for a role combination

chooses policies associated with the combination itself, policies

associated with each of its sub-combinations, and policies

associated with each of the individual roles in the role-

combination.

It is important to note that a role is more than an attribute. A

role defines a particular function of an entity or component that can

be used to identify particular behavior associated with that entity

or component. This difference is critical, and is most easily

understood by thinking of a role as a selector. When used in this

manner, one role (or role-combination) selects a different set of

policies than a different role (or role-combination) does.

Roles and role-combinations are especially useful in selecting which

policies are applicable to a particular set of entities or components

when the policy repository can store thousands or hundreds of

thousands of policies. This use emphasizes the ability of the role

(or role- combination) to select the small subset of policies that

are applicable from a huge set of policies that are available.

An example will illustrate how role-combinations actually work.

Suppose an installation has three roles defined for interfaces:

"Ethernet", "Campus", and "WAN". In the Policy Repository, some

policy rules could be associated with the role "Ethernet"; these

rules would apply to all Ethernet interfaces, regardless of whether

they were on the campus side or the WAN side. Other rules could be

associated with the role-combination "Campus"+"Ethernet"; these rules

would apply to the campus-side Ethernet interfaces, but not to those

on the WAN side. Finally, a third set of rules could be associated

with the role-combination "Ethernet"+"WAN"; these rules would apply

to the WAN-side Ethernet interfaces, but not to those on the campus

side. (The roles in a role-combination appear in alphabetical order

in these examples, because that is how they appear in the information

model.)

If we have a specific interface A that's associated with the role-

combination "Ethernet"+"WAN", we see that it should have three

categories of policy rules applied to it: those for the "Ethernet"

role, those for the "WAN" role, and those for the role-combination

"Ethernet"+"WAN". Going one step further, if interface B is

associated with the role- combination "branch-

Office"+"Ethernet"+"WAN", then B should have seven categories of

policy rules applied to it - those associated with the following

role-combinations:

o "branch-office"

o "Ethernet"

o "WAN"

o "branch-office"+"Ethernet"

o "branch-office"+"WAN"

o "Ethernet"+"WAN"

o "branch-office"+"Ethernet"+"WAN".

In order to get all of the right policy rules for a resource like

interface B, a PDP must expand the single role-combination it

receives for B into this list of seven role-combinations, and then

retrieve from the Policy Repository the corresponding seven sets of

policy rules. Of course this example is unusually complicated: the

normal case will involve expanding a two-role combination into three

values identifying three sets of policy rules.

Role-combinations also help to simplify somewhat the problem of

identifying conflicts between policy rules. With role-combinations,

it is possible for a policy administrator to specify one set of

policy rules for campus-side Ethernet interfaces, and a second set of

policy rules for WAN-side Ethernet interfaces, without having to

worry about conflicts between the two sets of rules. The policy

administrator simply "turns off" conflict detection for these two

sets of rules, by telling the policy management system that the roles

"Campus" and "WAN" are incompatible with each other. This indicates

that the role combination will never occur, and therefore conflicts

will never occur. In some cases the technology itself might identify

incompatible roles: "Ethernet" and "FrameRelay", for example. But

for less precise terms like "Campus" and "WAN", the policy

administrator must say whether they identify incompatible roles.

When the policy administrator does this, there are three effects:

1. If an interface has assigned to it a role-combination involving

both "Campus" and "WAN", then the policy management system can

flag it as an error.

2. If a policy rule is associated with a role-combination involving

both "Campus" and "WAN", then the policy management system can

flag it as an error.

3. If the policy management system sees two policy rules, where one

is tied to the role "Campus" (or to a role-combination that

includes the role "Campus") and the other is tied to the role

"WAN" (or to a role- combination that includes the role "WAN"),

then the system does not need to look for conflicts between the

two policy rules: because of the incompatible roles, the two

rules cannot possibly conflict.

+-------------------+

Policy Repository

+-------------------+

V

V retrieval of policy

V

+---------+

PDP/PEP

+---------+

v

v application of policy

v

+----------------+

Network Entity

+----------------+

Figure 4. Retrieval and Application of a Policy

Figure 4, which is introduced only as an example of how the Policy

Framework might be implemented by a collection of network

components, illustrates how roles operate within the Policy

Framework. Because the distinction between them is not important

to this discussion, the PDP and the PEP are combined in one box.

The points illustrated here apply equally well, though, to an

environment where the PDP and the PEP are implemented separately.

A role represents a functional characteristic or capability of a

resource to which policies are applied. Examples of roles include

Backbone interface, Frame Relay interface, BGP-capable router, web

server, firewall, etc. The multiple roles assigned to a single

resource are combined to form that resource's role combination.

Role combinations are represented in the PCIM by values of the

PolicyRoles property in the PolicyRule class. A PDP uses policy

roles as follows to identify the policies it needs to be aware of:

1. The PDP learns in some way the list of roles that its PEPs

play. This information might be configured at the PDP, the

PEPs might supply it to the PDP, or the PDP might retrieve it

from a repository.

2. Using repository-specific means, the PDP determines where to

look for policy rules that might apply to it.

3. Using the roles and role-combinations it received from its PEPs

as indicated in the examples above, the PDP is able to locate

and retrieve the policy rules that are relevant to it.

5.2.2. The PolicyRoles Property

As indicated earlier, PolicyRoles is a property associated with a

policy rule. It is an array holding "role combinations" for the

policy rule, and correlates with the roles defined for a network

resource. Using the PolicyRoles property, it is possible to mark a

policy rule as applying, for example, to a Frame Relay interface or

to a backbone ATM interface. The PolicyRoles property take strings

of the form:

<RoleName>[&&<RoleName>]*

Each value of this property represents a role combination, including

the special case of a "combination" containing only one role. As the

format indicates, the role names in a role combination are ANDed

together to form a single selector. The multiple values of the

PolicyRoles property are logically ORed, to make it possible for a

policy rule to have multiple selectors.

The individual role names in a role combination must appear in

alphabetical order (according to the collating sequence for UCS-2

characters), to make the string matches work correctly. The role

names used in an environment are specified by the policy

administrator.

5.3. Local Time and UTC Time in PolicyTimePeriodConditions

An instance of PolicyTimePeriodCondition has up to five properties

that represent times: TimePeriod, MonthOfYearMask, DayOfMonthMask,

DayOfWeekMask, and TimeOfDayMask. All of the time-related properties

in an instance of PolicyTimePeriodCondition represent one of two

types of times: local time at the place where a policy rule is

applied, or UTC time. The property LocalOrUtcTime indicates which

time representation applies to an instance of

PolicyTimePeriodCondition.

Since the PCIM provides only for local time and UTC time, a Policy

Management Tool that provides for other time representations (for

example, a fixed time at a particular location) will need to map from

these other representations to either local time or UTC time. An

example will illustrate the nature of this mapping.

Suppose a policy rule is tied to the hours of operation for a Help

Desk: 0800 to 2000 Monday through Friday [US] Eastern Time. In

order to express these times in PolicyTimePeriodCondition, a

management tool must convert them to UTC times. (They are not local

times, because they refer to a single time interval worldwide, not to

intervals tied to the local clocks at the locations where the

PolicyRule is being applied.) As reference [10] points out, mapping

from [US] Eastern Time to UTC time is not simply a matter of applying

an offset: the offset between [US] Eastern Time and UTC time

switches between -0500 and -0400 depending on whether Daylight

Savings Time is in effect in the US.

Suppose the policy administrator's goal is to have a policy rule be

valid from 0800 until 1200 [US] Eastern Time on every Monday, within

the overall time period from the beginning of 2000 until the end of

2001. The Policy Management Tool could either be configured with the

definition of what [US] Eastern Time means, or it could be configured

with knowledge of where to go to get this information. Reference

[10] contains further discussion of time zone definitions and where

they might reside.

Armed with knowledge about [US] Eastern Time, the Policy Management

Tool would create however many instances of PolicyTimePeriodCondition

it needed to represent the desired intervals. Note that while there

is an increased number of PolicyTimePeriodCondition instances, there

is still just one PolicyRule, which is tied to all the

PolicyTimePeriodCondition instances via the aggregation

PolicyRuleValidityPeriod. Here are the first two of these instances:

1. TimePeriod: 20000101T050000/20000402T070000

DayOfWeekMask: { Monday }

TimeOfDayMask: T130000/T170000

LocalOrUtcTime: UTC

2. TimePeriod: 20000402T070000/20001029T070000

DayOfWeekMask: { Monday }

TimeOfDayMask: T120000/T160000

LocalOrUtcTime: UTC

There would be three more similar instances, for winter 2000-2001,

summer 2001, and winter 2001 up through December 31.

Had the example been chosen differently, there could have been even

more instances of PolicyTimePeriodCondition. If, for example, the

time interval had been from 0800 - 2200 [US] Eastern Time on Mondays,

instance 1 above would have split into two instances: one with a UTC

time interval of T130000/T240000 on Mondays, and another with a UTC

time interval of T000000/T030000 on Tuesdays. So the end result

would have been ten instances of PolicyTimePeriodCondition, not five.

By restricting PolicyTimePeriodCondition to local time and UTC time,

the PCIM places the difficult and expensive task of mapping from

"human" time representations to machine-friendly ones in the Policy

Management Tool. Another approach would have been to place in

PolicyTimePeriodCondition a means of representing a named time zone,

such as [US] Eastern Time. This, however, would have passed the

difficult mapping responsibility down to the PDPs and PEPs. It is

better to have a mapping such as the one described above done once in

a Policy Management Tool, rather than having it done over and over in

each of the PDPs (and possibly PEPs) that need to apply a PolicyRule.

5.4. CIM Data Types

Since PCIM extends the CIM Schema, a correspondence between data

types used in both CIM and PCIM is needed. The following CIM data

types are used in the class definitions that follow in Sections 6 and

7:

o uint8 unsigned 8-bit integer

o uint16 unsigned 16-bit integer

o boolean Boolean

o string UCS-2 string.

Strings in CIM are stored as UCS-2 characters, where each character

is encoded in two octets. Thus string values may need to be

converted when moving between a CIM environment and one that uses a

different string encoding. For example, in an LDAP-accessible

directory, attributes of type DirectoryString are stored in UTF-8

format. RFC2279 [7] explains how to convert between these two

formats.

When it is applied to a CIM string, a MaxLen value refers to the

maximum number of characters in the string, rather than to the

maximum number of octets.

In addition to the CIM data types listed above, the association

classes in Section 7 use the following type:

o <classname> ref strongly typed reference.

There is one obvious omission from this list of CIM data types:

octet strings. This is because CIM treats octet strings as a derived

data type. There are two forms of octet strings in CIM - an ordered

uint8 array for single-valued strings, and a string array for multi-

valued properties. Both are described by adding an "OctetString"

qualifier (meta-data) to the property. This qualifier functions

exactly like an SMIv2 (SNMP) Textual Convention, refining the syntax

and semantics of the existing CIM data type.

The first four numeric elements of both of the "OctetString"

representations are a length field. (The reason that the "numeric"

adjective is added to the previous sentence is that the string

property also includes '0' and 'x', as its first characters.) In

both cases, these 4 numeric elements (octets) are included in

calculating the length. For example, a single-valued octet string

property having the value X'7C' would be represented by the uint8

array, X'00 00 00 05 7C'.

The strings representing the individual values of a multi-valued

property qualified with the "OctetString" qualifier are constructed

similarly:

1. Take a value to be encoded as an octet string (we'll use X'7C' as

above), and prepend to it a four-octet length. The result is the

same, X'00 00 00 05 7C'.

2. Convert this to a character string by introducing '0' and 'x' at

the front, and removing all white space. Thus we have the 12-

character string "0x000000057C". This string is the value of one

of the array elements in the CIM string array. Since CIM uses the

UCS-2 character set, it will require 24 octets to encode this 12-

character string.

Mappings of the PCIM to particular data models are not required to

follow this CIM technique of representing multi-valued octet strings

as length- prefixed character strings. In an LDAP mapping, for

example, it would be much more natural to simply use the Octet String

syntax, and omit the prepended length octets.

5.5. Comparison between CIM and LDAP Class Specifications

There are a number of differences between CIM and LDAP class

specifications. The ones that are relevant to the abbreviated class

specifications in this document are listed below. These items are

included here to help introduce the IETF community, which is already

familiar with LDAP, to CIM modeling, and by extension, to information

modeling in general.

o Instead of LDAP's three class types (abstract, auxiliary,

structural), CIM has only two: abstract and instantiable. The

type of a CIM class is indicated by the Boolean qualifier

ABSTRACT.

o CIM uses the term "property" for what LDAP terms an "attribute".

o CIM uses the array notation "[ ]" to indicate that a property is

multi-valued. CIM defines three types of arrays: bags (contents

are unordered, duplicates allowed), ordered bags (contents are

ordered but duplicates are allowed) and indexed arrays (contents

are ordered and no duplicates are allowed).

o CIM classes and properties are identified by name, not by OID.

o CIM classes use a different naming scheme for native

implementations, than LDAP. The CIM naming scheme is documented

in Appendix A since it is not critical to understanding the

information model, and only applies when communicating with a

native CIM implementation.

o In LDAP, attribute definitions are global, and the same attribute

may appear in multiple classes. In CIM, a property is defined

within the scope of a single class definition. The property may

be inherited into subclasses of the class in which it is defined,

but otherwise it cannot appear in other classes. One side effect

of this difference is that CIM property names tend to be much

shorter than LDAP attribute names, since they are implicitly

scoped by the name of the class in which they are defined.

There is also a notational convention that this document follows, to

improve readability. In CIM, all class and property names are

prefixed with the characters "CIM_". These prefixes have been

omitted throughout this document, with one exception regarding

naming, documented in Appendix A.

For the complete definition of the CIM specification language, see

reference [2].

6. Class Definitions

The following sections contain the definitions of the PCIM classes.

6.1. The Abstract Class "Policy"

The abstract class Policy collects several properties that may be

included in instances of any of the Core Policy classes (or their

subclasses). For convenience, the two properties that Policy

inherits from ManagedElement in the CIM schema are shown here as

well.

The class definition is as follows:

NAME Policy

DESCRIPTION An abstract class with four properties for

describing a policy-related instance.

DERIVED FROM ManagedElement

ABSTRACT TRUE

PROPERTIES CommonName (CN)

PolicyKeywords[ ]

// Caption (inherited)

// Description (inherited)

6.1.1. The Property "CommonName (CN)"

The CN, or CommonName, property corresponds to the X.500 attribute

commonName (cn). In X.500 this property specifies one or more user-

friendly names (typically only one name) by which an object is

commonly known, names that conform to the naming conventions of the

country or culture with which the object is associated. In the CIM

model, however, the CommonName property is single-valued.

NAME CN

DESCRIPTION A user-friendly name of a policy-related object.

SYNTAX string

6.1.2. The Multi-valued Property "PolicyKeywords"

This property provides a set of one or more keywords that a policy

administrator may use to assist in characterizing or categorizing a

policy object. Keywords are of one of two types:

o Keywords defined in this document, or in documents that define

subclasses of the classes defined in this document. These

keywords provide a vendor-independent, installation-independent

way of characterizing policy objects.

o Installation-dependent keywords for characterizing policy objects.

Examples include "Engineering", "Billing", and "Review in December

2000".

This document defines the following keywords: "UNKNOWN",

"CONFIGURATION", "USAGE", "SECURITY", "SERVICE", "MOTIVATIONAL",

"INSTALLATION", and "EVENT". These concepts were defined earlier in

Section 2.

One additional keyword is defined: "POLICY". The role of this

keyword is to identify policy-related instances that would not

otherwise be identifiable as being related to policy. It may be

needed in some repository implementations.

Documents that define subclasses of the Policy Core Information Model

classes SHOULD define additional keywords to characterize instances

of these subclasses. By convention, keywords defined in conjunction

with class definitions are in uppercase. Installation-defined

keywords can be in any case.

The property definition is as follows:

NAME PolicyKeywords

DESCRIPTION A set of keywords for characterizing /categorizing

policy objects.

SYNTAX string

6.1.3. The Property "Caption" (Inherited from ManagedElement)

This property provides a one-line description of a policy-related

object.

NAME Caption

DESCRIPTION A one-line description of this policy-related object.

SYNTAX string

6.1.4. The Property "Description" (Inherited from ManagedElement)

This property provides a longer description than that provided by the

caption property.

NAME Description

DESCRIPTION A long description of this policy-related object.

SYNTAX string

6.2. The Class "PolicyGroup"

This class is a generalized aggregation container. It enables either

PolicyRules or PolicyGroups to be aggregated in a single container.

Loops, including the degenerate case of a PolicyGroup that contains

itself, are not allowed when PolicyGroups contain other PolicyGroups.

PolicyGroups and their nesting capabilities are shown in Figure 5

below. Note that a PolicyGroup can nest other PolicyGroups, and

there is no restriction on the depth of the nesting in sibling

PolicyGroups.

+---------------------------------------------------+

PolicyGroup

+--------------------+ +-----------------+

PolicyGroup A PolicyGroup X

+----------------+ ooo

PolicyGroup A1

+----------------+

+--------------------+ +-----------------+

+---------------------------------------------------+

Figure 5. Overview of the PolicyGroup class

As a simple example, think of the highest level PolicyGroup shown in

Figure 5 above as a logon policy for US employees of a company. This

PolicyGroup may be called USEmployeeLogonPolicy, and may aggregate

several PolicyGroups that provide specialized rules per location.

Hence, PolicyGroup A in Figure 5 above may define logon rules for

employees on the West Coast, while another PolicyGroup might define

logon rules for the Midwest (e.g., PolicyGroup X), and so forth.

Note also that the depth of each PolicyGroup does not need to be the

same. Thus, the WestCoast PolicyGroup might have several additional

layers of PolicyGroups defined for any of several reasons (different

locales, number of subnets, etc..). The PolicyRules are therefore

contained at n levels from the USEmployeeLogonPolicyGroup. Compare

this to the Midwest PolicyGroup (PolicyGroup X), which might directly

contain PolicyRules.

The class definition for PolicyGroup is as follows:

NAME PolicyGroup

DESCRIPTION A container for either a set of related

PolicyRules or a set of related PolicyGroups.

DERIVED FROM Policy

ABSTRACT FALSE

PROPERTIES NONE

No properties are defined for this class since it inherits all its

properties from Policy. The class exists to aggregate PolicyRules or

other PolicyGroups. It is directly instantiable. In an

implementation, various key/identification properties MUST be

defined. The keys for a native CIM implementation are defined in

Appendix A, Section 13.1.1. Keys for an LDAP implementation will be

defined in the LDAP mapping of this information model [11].

6.3. The Class "PolicyRule"

This class represents the "If Condition then Action" semantics

associated with a policy. A PolicyRule condition, in the most

general sense, is represented as either an ORed set of ANDed

conditions (Disjunctive Normal Form, or DNF) or an ANDed set of ORed

conditions (Conjunctive Normal Form, or CNF). Individual conditions

may either be negated (NOT C) or unnegated (C). The actions

specified by a PolicyRule are to be performed if and only if the

PolicyRule condition (whether it is represented in DNF or CNF)

evaluates to TRUE.

The conditions and actions associated with a policy rule are modeled,

respectively, with subclasses of the classes PolicyCondition and

PolicyAction. These condition and action objects are tied to

instances of PolicyRule by the PolicyConditionInPolicyRule and

PolicyActionInPolicyRule aggregations.

As illustrated above in Section 3, a policy rule may also be

associated with one or more policy time periods, indicating the

schedule according to which the policy rule is active and inactive.

In this case it is the PolicyRuleValidityPeriod aggregation that

provides the linkage.

A policy rule is illustrated conceptually in Figure 6. below.

+------------------------------------------------+

PolicyRule

+--------------------+ +-----------------+

PolicyCondition(s) PolicyAction(s)

+--------------------+ +-----------------+

+------------------------------+

PolicyTimePeriodCondition(s)

+------------------------------+

+------------------------------------------------+

Figure 6. Overview of the PolicyRule Class

The PolicyRule class uses the property ConditionListType, to indicate

whether the conditions for the rule are in DNF or CNF. The

PolicyConditionInPolicyRule aggregation contains two additional

properties to complete the representation of the rule's conditional

expression. The first of these properties is an integer to partition

the referenced conditions into one or more groups, and the second is

a Boolean to indicate whether a referenced condition is negated. An

example shows how ConditionListType and these two additional

properties provide a unique representation of a set of conditions in

either DNF or CNF.

Suppose we have a PolicyRule that aggregates five PolicyConditions C1

through C5, with the following values in the properties of the five

PolicyConditionInPolicyRule associations:

C1: GroupNumber = 1, ConditionNegated = FALSE

C2: GroupNumber = 1, ConditionNegated = TRUE

C3: GroupNumber = 1, ConditionNegated = FALSE

C4: GroupNumber = 2, ConditionNegated = FALSE

C5: GroupNumber = 2, ConditionNegated = FALSE

If ConditionListType = DNF, then the overall condition for the

PolicyRule is:

(C1 AND (NOT C2) AND C3) OR (C4 AND C5)

On the other hand, if ConditionListType = CNF, then the overall

condition for the PolicyRule is:

(C1 OR (NOT C2) OR C3) AND (C4 OR C5)

In both cases, there is an unambiguous specification of the overall

condition that is tested to determine whether to perform the actions

associated with the PolicyRule.

The class definition is as follows:

NAME PolicyRule

DESCRIPTION The central class for representing the "If Condition

then Action" semantics associated with a policy rule.

DERIVED FROM Policy

ABSTRACT FALSE

PROPERTIES Enabled

ConditionListType

RuleUsage

Priority

Mandatory

SequencedActions

PolicyRoles

The PolicyRule class is directly instantiable. In an implementation,

various key/identification properties MUST be defined. The keys for

a native CIM implementation are defined in Appendix A, Section

13.1.2. Keys for an LDAP implementation will be defined in the LDAP

mapping of this information model [11].

6.3.1. The Property "Enabled"

This property indicates whether a policy rule is currently enabled,

from an administrative point of view. Its purpose is to allow a

policy administrator to enable or disable a policy rule without

having to add it to, or remove it from, the policy repository.

The property also supports the value 'enabledForDebug'. When the

property has this value, the entity evaluating the policy

condition(s) is being told to evaluate the conditions for the policy

rule, but not to perform the actions if the conditions evaluate to

TRUE. This value serves as a debug vehicle when attempting to

determine what policies would execute in a particular scenario,

without taking any actions to change state during the debugging.

The property definition is as follows:

NAME Enabled

DESCRIPTION An enumeration indicating whether a policy rule is

administratively enabled, administratively disabled,

or enabled for debug mode.

SYNTAX uint16

VALUES enabled(1), disabled(2), enabledForDebug(3)

DEFAULT VALUE enabled(1)

6.3.2. The Property "ConditionListType"

This property is used to specify whether the list of policy

conditions associated with this policy rule is in disjunctive normal

form (DNF) or conjunctive normal form (CNF). If this property is not

present, the list type defaults to DNF. The property definition is

as follows:

NAME ConditionListType

DESCRIPTION Indicates whether the list of policy conditions

associated with this policy rule is in disjunctive

normal form (DNF) or conjunctive normal form (CNF).

SYNTAX uint16

VALUES DNF(1), CNF(2)

DEFAULT VALUE DNF(1)

6.3.3. The Property "RuleUsage"

This property is a free-form string that recommends how this policy

should be used. The property definition is as follows:

NAME RuleUsage

DESCRIPTION This property is used to provide guidelines on

how this policy should be used.

SYNTAX string

6.3.4. The Property "Priority"

This property provides a non-negative integer for prioritizing policy

rules relative to each other. Larger integer values indicate higher

priority. Since one purpose of this property is to allow specific,

ad hoc policy rules to temporarily override established policy rules,

an instance that has this property set has a higher priority than all

instances that use or set the default value of zero.

Prioritization among policy rules provides a basic mechanism for

resolving policy conflicts.

The property definition is as follows:

NAME Priority

DESCRIPTION A non-negative integer for prioritizing this

PolicyRule relative to other PolicyRules. A larger

value indicates a higher priority.

SYNTAX uint16

DEFAULT VALUE 0

6.3.5. The Property "Mandatory"

This property indicates whether evaluation (and possibly action

execution) of a PolicyRule is mandatory or not. Its concept is

similar to the ability to mark packets for delivery or possible

discard, based on network traffic and device load.

The evaluation of a PolicyRule MUST be attempted if the Mandatory

property value is TRUE. If the Mandatory property value of a

PolicyRule is FALSE, then the evaluation of the rule is "best effort"

and MAY be ignored.

The property definition is as follows:

NAME Mandatory

DESCRIPTION A flag indicating that the evaluation of the

PolicyConditions and execution of PolicyActions

(if the condition list evaluates to TRUE) is

required.

SYNTAX boolean

DEFAULT VALUE TRUE

6.3.6. The Property "SequencedActions"

This property gives a policy administrator a way of specifying how

the ordering of the policy actions associated with this PolicyRule is

to be interpreted. Three values are supported:

o mandatory(1): Do the actions in the indicated order, or don't do

them at all.

o recommended(2): Do the actions in the indicated order if you can,

but if you can't do them in this order, do them in another order

if you can.

o dontCare(3): Do them -- I don't care about the order.

When error / event reporting is addressed for the Policy Framework,

suitable codes will be defined for reporting that a set of actions

could not be performed in an order specified as mandatory (and thus

were not performed at all), that a set of actions could not be

performed in a recommended order (and moreover could not be performed

in any order), or that a set of actions could not be performed in a

recommended order (but were performed in a different order). The

property definition is as follows:

NAME SequencedActions

DESCRIPTION An enumeration indicating how to interpret the

action ordering indicated via the

PolicyActionInPolicyRule aggregation.

SYNTAX uint16

VALUES mandatory(1), recommended(2), dontCare(3)

DEFAULT VALUE dontCare(3)

6.3.7. The Multi-valued Property "PolicyRoles"

This property represents the roles and role combinations associated

with a policy rule. Each value represents one role combination.

Since this is a multi-valued property, more than one role combination

can be associated with a single policy rule. Each value is a string

of the form

<RoleName>[&&<RoleName>]*

where the individual role names appear in alphabetical order

(according to the collating sequence for UCS-2). The property

definition is as follows:

NAME PolicyRoles

DESCRIPTION A set of strings representing the roles and role

combinations associated with a policy rule. Each

value represents one role combination.

SYNTAX string

6.4. The Abstract Class "PolicyCondition"

The purpose of a policy condition is to determine whether or not the

set of actions (aggregated in the PolicyRule that the condition

applies to) should be executed or not. For the purposes of the

Policy Core Information Model, all that matters about an individual

PolicyCondition is that it evaluates to TRUE or FALSE. (The

individual PolicyConditions associated with a PolicyRule are combined

to form a compound expression in either DNF or CNF, but this is

accomplished via the ConditionListType property, discussed above, and

by the properties of the PolicyConditionInPolicyRule aggregation,

introduced above and discussed further in Section 7.6 below.) A

logical structure within an individual PolicyCondition may also be

introduced, but this would have to be done in a subclass of

PolicyCondition.

Because it is general, the PolicyCondition class does not itself

contain any "real" conditions. These will be represented by

properties of the domain-specific subclasses of PolicyCondition.

+---------------------------------------------------------------+

Policy Conditions in DNF

+-------------------------+ +-----------------------+

AND list AND list

+-------------------+ +-----------------+

PolicyCondition PolicyCondition

+-------------------+ +-----------------+

+-------------------+ +-----------------+

PolicyCondition ... PolicyCondition

+-------------------+ ORed +-----------------+

... ...

ANDed ANDed

+-------------------+ +-----------------+

PolicyCondition PolicyCondition

+-------------------+ +-----------------+

+-------------------------+ +-----------------------+

+---------------------------------------------------------------+

Figure 7. Overview of Policy Conditions in DNF

This figure illustrates that when policy conditions are in DNF, there

are one or more sets of conditions that are ANDed together to form

AND lists. An AND list evaluates to TRUE if and only if all of its

constituent conditions evaluate to TRUE. The overall condition then

evaluates to TRUE if and only if at least one of its constituent AND

lists evaluates to TRUE.

+---------------------------------------------------------------+

Policy Conditions in CNF

+-------------------------+ +-----------------------+

OR list OR list

+-------------------+ +-----------------+

PolicyCondition PolicyCondition

+-------------------+ +-----------------+

+-------------------+ +-----------------+

PolicyCondition ... PolicyCondition

+-------------------+ ANDed +-----------------+

... ...

ORed ORed

+-------------------+ +-----------------+

PolicyCondition PolicyCondition

+-------------------+ +-----------------+

+-------------------------+ +-----------------------+

+---------------------------------------------------------------+

Figure 8. Overview of Policy Conditions in CNF

In this figure, the policy conditions are in CNF. Consequently,

there are one or more OR lists, each of which evaluates to TRUE if

and only if at least one of its constituent conditions evaluates to

TRUE. The overall condition then evaluates to TRUE if and only if

ALL of its constituent OR lists evaluate to TRUE.

The class definition of PolicyCondition is as follows:

NAME PolicyCondition

DESCRIPTION A class representing a rule-specific or reusable

policy condition to be evaluated in conjunction

with a policy rule.

DERIVED FROM Policy

ABSTRACT TRUE

PROPERTIES NONE

No properties are defined for this class since it inherits all its

properties from Policy. The class exists as an abstract superclass

for domain-specific policy conditions, defined in subclasses. In an

implementation, various key/identification properties MUST be defined

for the class or its instantiable subclasses. The keys for a native

CIM implementation are defined in Appendix A, Section 13.2. Keys for

an LDAP implementation will be defined in the LDAP mapping of this

information model [11].

When identifying and using the PolicyCondition class, it is necessary

to remember that a condition can be rule-specific or reusable. This

was discussed above in Section 5.1. The distinction between the two

types of policy conditions lies in the associations in which an

instance can participate, and in how the different instances are

named. Conceptually, a reusable policy condition resides in a policy

repository, and is named within the scope of that repository. On the

other hand, a rule-specific policy condition is, as the name

suggests, named within the scope of the single policy rule to which

it is related.

The distinction between rule-specific and reusable PolicyConditions

affects the CIM naming, defined in Appendix A, and the LDAP mapping

[11].

6.5. The Class "PolicyTimePeriodCondition"

This class provides a means of representing the time periods during

which a policy rule is valid, i.e., active. At all times that fall

outside these time periods, the policy rule has no effect. A policy

rule is treated as valid at all times if it does not specify a

PolicyTimePeriodCondition.

In some cases a PDP may need to perform certain setup / cleanup

actions when a policy rule becomes active / inactive. For example,

sessions that were established while a policy rule was active might

need to be taken down when the rule becomes inactive. In other

cases, however, such sessions might be left up: in this case, the

effect of deactivating the policy rule would just be to prevent the

establishment of new sessions. Setup / cleanup behaviors on validity

period transitions are not currently addressed by the PCIM, and must

be specified in 'guideline' documents, or via subclasses of

PolicyRule, PolicyTimePeriodCondition or other concrete subclasses of

Policy. If such behaviors need to be under the control of the policy

administrator, then a mechanism to allow this control must also be

specified in the subclass.

PolicyTimePeriodCondition is defined as a subclass of

PolicyCondition. This is to allow the inclusion of time-based

criteria in the AND/OR condition definitions for a PolicyRule.

Instances of this class may have up to five properties identifying

time periods at different levels. The values of all the properties

present in an instance are ANDed together to determine the validity

period(s) for the instance. For example, an instance with an overall

validity range of January 1, 2000 through December 31, 2000; a month

mask that selects March and April; a day-of-the-week mask that

selects Fridays; and a time of day range of 0800 through 1600 would

represent the following time periods:

Friday, March 5, 2000, from 0800 through 1600;

Friday, March 12, 2000, from 0800 through 1600;

Friday, March 19, 2000, from 0800 through 1600;

Friday, March 26, 2000, from 0800 through 1600;

Friday, April 2, 2000, from 0800 through 1600;

Friday, April 9, 2000, from 0800 through 1600;

Friday, April 16, 2000, from 0800 through 1600;

Friday, April 23, 2000, from 0800 through 1600;

Friday, April 30, 2000, from 0800 through 1600.

Properties not present in an instance of PolicyTimePeriodCondition

are implicitly treated as having their value "always enabled". Thus,

in the example above, the day-of-the-month mask is not present, and

so the validity period for the instance implicitly includes a day-

of-the-month mask that selects all days of the month. If we apply

this "missing property" rule to its fullest, we see that there is a

second way to indicate that a policy rule is always enabled: have it

point to an instance of PolicyTimePeriodCondition whose only

properties are its naming properties.

The property LocalOrUtcTime indicates whether the times represented

in the other five time-related properties of an instance of

PolicyTimePeriodCondition are to be interpreted as local times for

the location where a policy rule is being applied, or as UTC times.

The class definition is as follows.

NAME PolicyTimePeriodCondition

DESCRIPTION A class that provides the capability of enabling /

disabling a policy rule according to a

pre-determined schedule.

DERIVED FROM PolicyCondition

ABSTRACT FALSE

PROPERTIES TimePeriod

MonthOfYearMask

DayOfMonthMask

DayOfWeekMask

TimeOfDayMask

LocalOrUtcTime

6.5.1. The Property "TimePeriod"

This property identifies an overall range of calendar dates and times

over which a policy rule is valid. It reuses the format for an

explicit time period defined in RFC2445 (reference [10]): a string

representing a starting date and time, in which the character 'T'

indicates the beginning of the time portion, followed by the solidus

character '/', followed by a similar string representing an end date

and time. The first date indicates the beginning of the range, while

the second date indicates the end. Thus, the second date and time

must be later than the first. Date/times are expressed as substrings

of the form "yyyymmddThhmmss". For example:

20000101T080000/20000131T120000

January 1, 2000, 0800 through January 31, 2000, noon

There are also two special cases in which one of the date/time

strings is replaced with a special string defined in RFC2445.

o If the first date/time is replaced with the string "THISANDPRIOR",

then the property indicates that a policy rule is valid [from now]

until the date/time that appears after the '/'.

o If the second date/time is replaced with the string

"THISANDFUTURE", then the property indicates that a policy rule

becomes valid on the date/time that appears before the '/', and

remains valid from that point on.

Note that RFC2445 does not use these two strings in connection with

explicit time periods. Thus the PCIM is combining two elements from

RFC2445 that are not combined in the RFCitself.

The property definition is as follows:

NAME TimePeriod

DESCRIPTION The range of calendar dates on which a policy

rule is valid.

SYNTAX string

FORMAT yyyymmddThhmmss/yyyymmddThhmmss, where the first

date/time may be replaced with the string

"THISANDPRIOR" or the second date/time may be

replaced with the string "THISANDFUTURE"

6.5.2. The Property "MonthOfYearMask"

The purpose of this property is to refine the definition of the valid

time period that is defined by the TimePeriod property, by explicitly

specifying the months when the policy is valid. These properties

work together, with the TimePeriod used to specify the overall time

period during which the policy might be valid, and the

MonthOfYearMask used to pick out the specific months within that time

period when the policy is valid.

This property is formatted as an octet string of size 2, consisting

of 12 bits identifying the 12 months of the year, beginning with

January and ending with December, followed by 4 bits that are always

set to '0'. For each month, the value '1' indicates that the policy

is valid for that month, and the value '0' indicates that it is not

valid. The value X'08 30', for example, indicates that a policy rule

is valid only in the months May, November, and December.

See section 5.4 for details of how CIM represents a single-valued

octet string property such as this one. (Basically, CIM prepends a

4-octet length to the octet string.)

If this property is omitted, then the policy rule is treated as valid

for all twelve months. The property definition is as follows:

NAME MonthOfYearMask

DESCRIPTION A mask identifying the months of the year in

which a policy rule is valid.

SYNTAX octet string

FORMAT X'hh h0'

6.5.3. The Property "DayOfMonthMask"

The purpose of this property is to refine the definition of the valid

time period that is defined by the TimePeriod property, by explicitly

specifying the days of the month when the policy is valid. These

properties work together, with the TimePeriod used to specify the

overall time period during which the policy might be valid, and the

DayOfMonthMask used to pick out the specific days of the month within

that time period when the policy is valid.

This property is formatted as an octet string of size 8, consisting

of 31 bits identifying the days of the month counting from the

beginning, followed by 31 more bits identifying the days of the month

counting from the end, followed by 2 bits that are always set to '0'.

For each day, the value '1' indicates that the policy is valid for

that day, and the value '0' indicates that it is not valid.

The value X'80 00 00 01 00 00 00 00', for example, indicates that a

policy rule is valid on the first and last days of the month.

For months with fewer than 31 days, the digits corresponding to days

that the months do not have (counting in both directions) are

ignored.

The encoding of the 62 significant bits in the octet string matches

that used for the schedDay object in the DISMAN-SCHEDULE-MIB. See

reference [8] for more details on this object.

See section 5.4 for details of how CIM represents a single-valued

octet string property such as this one. (Basically, CIM prepends a

4-octet length to the octet string.)

The property definition is as follows:

NAME DayOfMonthMask

DESCRIPTION A mask identifying the days of the month on

which a policy rule is valid.

SYNTAX octet string

FORMAT X'hh hh hh hh hh hh hh hh'

6.5.4. The Property "DayOfWeekMask"

The purpose of this property is to refine the definition of the valid

time period that is defined by the TimePeriod property by explicitly

specifying the days of the week when the policy is valid. These

properties work together, with the TimePeriod used to specify the

overall time period when the policy might be valid, and the

DayOfWeekMask used to pick out the specific days of the week in that

time period when the policy is valid.

This property is formatted as an octet string of size 1, consisting

of 7 bits identifying the 7 days of the week, beginning with Sunday

and ending with Saturday, followed by 1 bit that is always set to

'0'. For each day of the week, the value '1' indicates that the

policy is valid for that day, and the value '0' indicates that it is

not valid.

The value X'7C', for example, indicates that a policy rule is valid

Monday through Friday.

See section 5.4 for details of how CIM represents a single-valued

octet string property such as this one. (Basically, CIM prepends a

4-octet length to the octet string.)

The property definition is as follows:

NAME DayOfWeekMask

DESCRIPTION A mask identifying the days of the week on which

a policy rule is valid.

SYNTAX octet string

FORMAT B'bbbb bbb0'

6.5.5. The Property "TimeOfDayMask"

The purpose of this property is to refine the definition of the valid

time period that is defined by the TimePeriod property by explicitly

specifying a range of times in a day the policy is valid for. These

properties work together, with the TimePeriod used to specify the

overall time period that the policy is valid for, and the

TimeOfDayMask used to pick out which range of time periods in a given

day of that time period the policy is valid for.

This property is formatted in the style of RFC2445 [10]: a time

string beginning with the character 'T', followed by the solidus

character '/', followed by a second time string. The first time

indicates the beginning of the range, while the second time indicates

the end. Times are expressed as substrings of the form "Thhmmss".

The second substring always identifies a later time than the first

substring. To allow for ranges that span midnight, however, the

value of the second string may be smaller than the value of the first

substring. Thus, "T080000/T210000" identifies the range from 0800

until 2100, while "T210000/T080000" identifies the range from 2100

until 0800 of the following day.

When a range spans midnight, it by definition includes parts of two

successive days. When one of these days is also selected by either

the MonthOfYearMask, DayOfMonthMask, and/or DayOfWeekMask, but the

other day is not, then the policy is active only during the portion

of the range that falls on the selected day. For example, if the

range extends from 2100 until 0800, and the day of week mask selects

Monday and Tuesday, then the policy is active during the following

three intervals:

From midnight Sunday until 0800 Monday;

From 2100 Monday until 0800 Tuesday;

From 2100 Tuesday until 23:59:59 Tuesday.

The property definition is as follows:

NAME TimeOfDayMask

DESCRIPTION The range of times at which a policy rule is

valid. If the second time is earlier than the

first, then the interval spans midnight.

SYNTAX string

FORMAT Thhmmss/Thhmmss

6.5.6. The Property "LocalOrUtcTime"

This property indicates whether the times represented in the

TimePeriod property and in the various Mask properties represent

local times or UTC times. There is no provision for mixing of local

times and UTC times: the value of this property applies to all of

the other time-related properties.

The property definition is as follows:

NAME LocalOrUtcTime

DESCRIPTION An indication of whether the other times in this

instance represent local times or UTC times.

SYNTAX uint16

VALUES localTime(1), utcTime(2)

DEFAULT VALUE utcTime(2)

6.6. The Class "VendorPolicyCondition"

The purpose of this class is to provide a general extension mechanism

for representing policy conditions that have not been modeled with

specific properties. Instead, the two properties Constraint and

ConstraintEncoding are used to define the content and format of the

condition, as explained below.

As its name suggests, this class is intended for vendor-specific

extensions to the Policy Core Information Model. Standardized

extensions are not expected to use this class.

The class definition is as follows:

NAME VendorPolicyCondition

DESCRIPTION A class that defines a registered means to

describe a policy condition.

DERIVED FROM PolicyCondition

ABSTRACT FALSE

PROPERTIES Constraint[ ]

ConstraintEncoding

6.6.1. The Multi-valued Property "Constraint"

This property provides a general extension mechanism for representing

policy conditions that have not been modeled with specific

properties. The format of the octet strings in the array is left

unspecified in this definition. It is determined by the OID value

stored in the property ConstraintEncoding. Since ConstraintEncoding

is single-valued, all the values of Constraint share the same format

and semantics.

See Section 5.4 for a description of how CIM encodes an array of

octet strings like this one.

A policy decision point can readily determine whether it supports the

values stored in an instance of Constraint by checking the OID value

from ConstraintEncoding against the set of OIDs it recognizes. The

action for the policy decision point to take in case it does not

recognize the format of this data could itself be modeled as a policy

rule, governing the behavior of the policy decision point.

The property is defined as follows:

NAME Constraint

DESCRIPTION Extension mechanism for representing constraints

that have not been modeled as specific

properties. The format of the values is

identified by the OID stored in the property

ConstraintEncoding.

SYNTAX octet string

6.6.2. The Property "ConstraintEncoding"

This property identifies the encoding and semantics of the Constraint

property values in this instance. The value of this property is a

single string, representing a single OID.

The property is defined as follows:

NAME ConstraintEncoding

DESCRIPTION An OID encoded as a string, identifying the format

and semantics for this instance's Constraint

property. The value is a dotted sequence of

decimal digits (for example, "1.2.100.200")

representing the arcs of the OID. The characters

in the string are the UCS-2 characters

corresponding to the US ASCII encodings of the

numeric characters and the period.

SYNTAX string

6.7. The Abstract Class "PolicyAction"

The purpose of a policy action is to execute one or more operations

that will affect network traffic and/or systems, devices, etc., in

order to achieve a desired state. This (new) state provides one or

more (new) behaviors. A policy action ordinarily changes the

configuration of one or more elements.

A PolicyRule contains one or more policy actions. A policy

administrator can assign an order to the actions associated with a

PolicyRule, complete with an indication of whether the indicated

order is mandatory, recommended, or of no significance. Ordering of

the actions associated with a PolicyRule is accomplished via a

property in the PolicyActionInPolicyRule aggregation.

The actions associated with a PolicyRule are executed if and only if

the overall condition(s) of the PolicyRule evaluates to TRUE.

The class definition of PolicyAction is as follows:

NAME PolicyAction

DESCRIPTION A class representing a rule-specific or reusable

policy action to be performed if the condition for

a policy rule evaluates to TRUE.

DERIVED FROM Policy

ABSTRACT TRUE

PROPERTIES NONE

No properties are defined for this class since it inherits all its

properties from Policy. The class exists as an abstract superclass

for domain-specific policy actions, defined in subclasses. In an

implementation, various key/identification properties MUST be defined

for the class or its instantiable subclasses. The keys for a native

CIM implementation are defined in Appendix A, Section 13.3. Keys for

an LDAP implementation will be defined in the LDAP mapping of this

information model [11].

When identifying and using the PolicyAction class, it is necessary to

remember that an action can be rule-specific or reusable. This was

discussed above in Section 5.1. The distinction between the two

types of policy actions lies in the associations in which an instance

can participate, and in how the different instances are named.

Conceptually, a reusable policy action resides in a policy

repository, and is named within the scope of that repository. On the

other hand, a rule-specific policy action is named within the scope

of the single policy rule to which it is related.

The distinction between rule-specific and reusable PolicyActions

affects the CIM naming, defined in Appendix A, and the LDAP mapping

[11].

6.8. The Class "VendorPolicyAction"

The purpose of this class is to provide a general extension mechanism

for representing policy actions that have not been modeled with

specific properties. Instead, the two properties ActionData and

ActionEncoding are used to define the content and format of the

action, as explained below.

As its name suggests, this class is intended for vendor-specific

extensions to the Policy Core Information Model. Standardized

extensions are not expected to use this class.

The class definition is as follows:

NAME VendorPolicyAction

DESCRIPTION A class that defines a registered means to

describe a policy action.

DERIVED FROM PolicyAction

ABSTRACT FALSE

PROPERTIES ActionData[ ]

ActionEncoding

6.8.1. The Multi-valued Property "ActionData"

This property provides a general extension mechanism for representing

policy actions that have not been modeled with specific properties.

The format of the octet strings in the array is left unspecified in

this definition. It is determined by the OID value stored in the

property ActionEncoding. Since ActionEncoding is single-valued, all

the values of ActionData share the same format and semantics. See

Section 5.4 for a discussion of how CIM encodes an array of octet

strings like this one.

A policy decision point can readily determine whether it supports the

values stored in an instance of ActionData by checking the OID value

from ActionEncoding against the set of OIDs it recognizes. The

action for the policy decision point to take in case it does not

recognize the format of this data could itself be modeled as a policy

rule, governing the behavior of the policy decision point.

The property is defined as follows:

NAME ActionData

DESCRIPTION Extension mechanism for representing actions that

have not been modeled as specific properties. The

format of the values is identified by the OID

stored in the property ActionEncoding.

SYNTAX octet string

6.8.2. The Property "ActionEncoding"

This property identifies the encoding and semantics of the ActionData

property values in this instance. The value of this property is a

single string, representing a single OID.

The property is defined as follows:

NAME ActionEncoding

DESCRIPTION An OID encoded as a string, identifying the format

and semantics for this instance's ActionData

property. The value is a dotted sequence of

decimal digits (for example, "1.2.100.200")

representing the arcs of the OID. The characters

in the string are the UCS-2 characters

corresponding to the US ASCII encodings of the

numeric characters and the period.

SYNTAX string

6.9. The Class "PolicyRepository"

The class definition of PolicyRepository is as follows:

NAME PolicyRepository

DESCRIPTION A class representing an administratively defined

container for reusable policy-related

information. This class does not introduce any

additional properties beyond those in its

superclass AdminDomain. It does, however,

participate in a number of unique associations.

DERIVED FROM AdminDomain

ABSTRACT FALSE

7. Association and Aggregation Definitions

The first two subsections of this section introduce associations and

aggregations as they are used in CIM. The remaining subsections

present the class definitions for the associations and aggregations

that are part of the Policy Core Information Model.

7.1. Associations

An association is a CIM construct representing a relationship between

two (or theoretically more) objects. It is modeled as a class

containing typically two object references. Associations can be

defined between classes without affecting any of the related classes.

That is, addition of an association does not affect the interface of

the related classes.

7.2. Aggregations

An aggregation is a strong form of an association, which usually

represents a "whole-part" or a "collection" relationship. For

example, CIM uses an aggregation to represent the containment

relationship between a system and the components that make up the

system. Aggregation as a "whole-part" relationship often implies,

but does not require, that the aggregated objects have mutual

dependencies.

7.3. The Abstract Aggregation "PolicyComponent

This abstract aggregation defines two object references that will be

overridden in each of five subclasses, to become references to the

concrete policy classes PolicyGroup, PolicyRule, PolicyCondition,

PolicyAction, and PolicyTimePeriodCondition. The value of the

abstract superclass is to convey that all five subclasses have the

same "whole- part" semantics, and for ease of query to locate all

"components" of a PolicyGroup or PolicyRule.

The class definition for the aggregation is as follows:

NAME PolicyComponent

DESCRIPTION A generic aggregation used to establish 'part of'

relationships between the subclasses of

Policy. For example, the

PolicyConditionInPolicyRule aggregation defines

that PolicyConditions are part of a PolicyRule.

ABSTRACT TRUE

PROPERTIES GroupComponent[ref Policy[0..n]]

PartComponent[ref Policy[0..n]]

7.4. The Aggregation "PolicyGroupInPolicyGroup"

The PolicyGroupInPolicyGroup aggregation enables policy groups to be

nested. This is critical for scalability and manageability, as it

enables complex policies to be constructed from multiple simpler

policies for administrative convenience. For example, a policy group

representing policies for the US might have nested within it policy

groups for the Eastern and Western US.

A PolicyGroup may aggregate other PolicyGroups via this aggregation,

or it may aggregate PolicyRules via the PolicyRuleInPolicyGroup

aggregation. Note that it is assumed that this aggregation is used

to form directed acyclic graphs and NOT ring structures.The class

definition for the aggregation is as follows:

NAME PolicyGroupInPolicyGroup

DESCRIPTION A class representing the aggregation of

PolicyGroups by a higher-level PolicyGroup.

DERIVED FROM PolicyComponent

ABSTRACT FALSE

PROPERTIES GroupComponent[ref PolicyGroup[0..n]]

PartComponent[ref PolicyGroup[0..n]]

7.4.1. The Reference "GroupComponent"

This property is inherited from PolicyComponent, and overridden to

become an object reference to a PolicyGroup that contains one or more

other PolicyGroups. Note that for any single instance of the

aggregation class PolicyGroupInPolicyGroup, this property (like all

Reference properties) is single-valued. The [0..n] cardinality

indicates that there may be 0, 1, or more than one PolicyGroups that

contain any given PolicyGroup.

7.4.2. The Reference "PartComponent"

This property is inherited from PolicyComponent, and overridden to

become an object reference to a PolicyGroup contained by one or more

other PolicyGroups. Note that for any single instance of the

aggregation class PolicyGroupInPolicyGroup, this property (like all

Reference properties) is single-valued. The [0..n] cardinality

indicates that a given PolicyGroup may contain 0, 1, or more than one

other PolicyGroups.

7.5. The Aggregation "PolicyRuleInPolicyGroup"

A policy group may aggregate one or more policy rules, via the

PolicyRuleInPolicyGroup aggregation. Grouping of policy rules into a

policy group is again for administrative convenience; a policy rule

may also be used by itself, without belonging to a policy group.

A PolicyGroup may aggregate PolicyRules via this aggregation, or it

may aggregate other PolicyGroups via the PolicyGroupInPolicyGroup

aggregation.

The class definition for the aggregation is as follows:

NAME PolicyRuleInPolicyGroup

DESCRIPTION A class representing the aggregation of

PolicyRules by a PolicyGroup.

DERIVED FROM PolicyComponent

ABSTRACT FALSE

PROPERTIES GroupComponent[ref PolicyGroup[0..n]]

PartComponent[ref PolicyRule[0..n]]

7.5.1. The Reference "GroupComponent"

This property is inherited from PolicyComponent, and overridden to

become an object reference to a PolicyGroup that contains one or more

PolicyRules. Note that for any single instance of the aggregation

class PolicyRuleInPolicyGroup, this property (like all Reference

properties) is single-valued. The [0..n] cardinality indicates that

there may be 0, 1, or more than one PolicyGroups that contain any

given PolicyRule.

7.5.2. The Reference "PartComponent"

This property is inherited from PolicyComponent, and overridden to

become an object reference to a PolicyRule contained by one or more

PolicyGroups. Note that for any single instance of the aggregation

class PolicyRuleInPolicyGroup, this property (like all Reference

properties) is single-valued. The [0..n] cardinality indicates that

a given PolicyGroup may contain 0, 1, or more than one PolicyRules.

7.6. The Aggregation "PolicyConditionInPolicyRule"

A policy rule aggregates zero or more instances of the

PolicyCondition class, via the PolicyConditionInPolicyRule

association. A policy rule that aggregates zero policy conditions

must indicate in its class definition what "triggers" the performance

of its actions. In short, it must describe its implicit

PolicyConditions, since none are explicitly associated. For example,

there might be a subclass of PolicyRule named "HttpPolicyRule", where

the class definition assumes that the condition, "If HTTP traffic,"

is true before the rule's actions would be performed. There is no

need to formalize and instantiate this condition, since it is obvious

in the semantics of the PolicyRule.

The conditions aggregated by a policy rule are grouped into two

levels of lists: either an ORed set of ANDed sets of conditions (DNF,

the default) or an ANDed set of ORed sets of conditions (CNF).

Individual conditions in these lists may be negated. The property

ConditionListType (in PolicyRule) specifies which of these two

grouping schemes applies to a particular PolicyRule. The conditions

are used to determine whether to perform the actions associated with

the PolicyRule.

One or more policy time periods may be among the conditions

associated with a policy rule via the PolicyConditionInPolicyRule

association. In this case, the time periods are simply additional

conditions to be evaluated along with any other conditions specified

for the rule.

The class definition for the aggregation is as follows:

NAME PolicyConditionInPolicyRule

DESCRIPTION A class representing the aggregation of

PolicyConditions by a PolicyRule.

DERIVED FROM PolicyComponent

ABSTRACT FALSE

PROPERTIES GroupComponent[ref PolicyRule[0..n]]

PartComponent[ref PolicyCondition[0..n]]

GroupNumber

ConditionNegated

7.6.1. The Reference "GroupComponent"

This property is inherited from PolicyComponent, and overridden to

become an object reference to a PolicyRule that contains one or more

PolicyConditions. Note that for any single instance of the

aggregation class PolicyConditionInPolicyRule, this property (like

all Reference properties) is single-valued. The [0..n] cardinality

indicates that there may be 0, 1, or more than one PolicyRules that

contain any given PolicyCondition.

7.6.2. The Reference "PartComponent"

This property is inherited from PolicyComponent, and overridden to

become an object reference to a PolicyCondition contained by one or

more PolicyRules. Note that for any single instance of the

aggregation class PolicyConditionInPolicyRule, this property (like

all Reference properties) is single-valued. The [0..n] cardinality

indicates that a given PolicyRule may contain 0, 1, or more than one

PolicyConditions.

7.6.3. The Property "GroupNumber"

This property contains an integer identifying the group to which the

condition referenced by the PartComponent property is assigned in

forming the overall conditional expression for the policy rule

identified by the GroupComponent reference.

The property is defined as follows:

NAME GroupNumber

DESCRIPTION Unsigned integer indicating the group to which

the condition identified by the PartComponent

property is to be assigned.

SYNTAX uint16

DEFAULT 0

7.6.4. The Property "ConditionNegated"

This property is a boolean, indicating whether the condition

referenced by the PartComponent property is negated in forming the

overall conditional expression for the policy rule identified by the

GroupComponent reference.

The property is defined as follows:

NAME ConditionNegated

DESCRIPTION Indication of whether the condition identified by

the PartComponent property is negated. (TRUE

indicates that the condition is negated, FALSE

indicates that it is not negated.)

SYNTAX boolean

DEFAULT FALSE

7.7. The Aggregation "PolicyRuleValidityPeriod"

A different relationship between a policy rule and a policy time

period (than PolicyConditionInPolicyRule) is represented by the

PolicyRuleValidityPeriod aggregation. The latter describes scheduled

activation and deactivation of the policy rule.

If a policy rule is associated with multiple policy time periods via

this association, then the rule is active if at least one of the time

periods indicates that it is active. (In other words, the time

periods are ORed to determine whether the rule is active.) A policy

time period may be aggregated by multiple policy rules. A rule that

does not point to a policy time period via this aggregation is, from

the point of view of scheduling, always active. It may, however, be

inactive for other reasons.

Time periods are a general concept that can be used in other

applications. However, they are mentioned explicitly here in this

specification since they are frequently used in policy applications.

The class definition for the aggregation is as follows:

NAME PolicyRuleValidityPeriod

DESCRIPTION A class representing the aggregation of

PolicyTimePeriodConditions by a PolicyRule.

DERIVED FROM PolicyComponent

ABSTRACT FALSE

PROPERTIES GroupComponent[ref PolicyRule[0..n]]

PartComponent[ref PolicyTimePeriodCondition[0..n]]

7.7.1. The Reference "GroupComponent"

This property is inherited from PolicyComponent, and overridden to

become an object reference to a PolicyRule that contains one or more

PolicyTimePeriodConditions. Note that for any single instance of the

aggregation class PolicyRuleValidityPeriod, this property (like all

Reference properties) is single-valued. The [0..n] cardinality

indicates that there may be 0, 1, or more than one PolicyRules that

contain any given PolicyTimePeriodCondition.

7.7.2. The Reference "PartComponent"

This property is inherited from PolicyComponent, and overridden to

become an object reference to a PolicyTimePeriodCondition contained

by one or more PolicyRules. Note that for any single instance of the

aggregation class PolicyRuleValidityPeriod, this property (like all

Reference properties) is single-valued. The [0..n] cardinality

indicates that a given PolicyRule may contain 0, 1, or more than one

PolicyTimePeriodConditions.

7.8. The Aggregation "PolicyActionInPolicyRule"

A policy rule may aggregate zero or more policy actions. A policy

rule that aggregates zero policy actions must indicate in its class

definition what actions are taken when the rule's conditions evaluate

to TRUE. In short, it must describe its implicit PolicyActions,

since none are explicitly associated. For example, there might be a

subclass of PolicyRule representing a Diffserv absolute dropper,

where the subclass itself indicates the action to be taken. There is

no need to formalize and instantiate this action, since it is obvious

in the semantics of the PolicyRule.

The actions associated with a PolicyRule may be given a required

order, a recommended order, or no order at all. For actions

represented as separate objects, the PolicyActionInPolicyRule

aggregation can be used to express an order.

This aggregation does not indicate whether a specified action order

is required, recommended, or of no significance; the property

SequencedActions in the aggregating instance of PolicyRule provides

this indication.

The class definition for the aggregation is as follows:

NAME PolicyActionInPolicyRule

DESCRIPTION A class representing the aggregation of

PolicyActions by a PolicyCondition.

DERIVED FROM PolicyComponent

ABSTRACT FALSE

PROPERTIES GroupComponent[ref PolicyRule[0..n]]

PartComponent[ref PolicyAction[0..n]]

ActionOrder

7.8.1. The Reference "GroupComponent"

This property is inherited from PolicyComponent, and overridden to

become an object reference to a PolicyRule that contains one or more

PolicyActions. Note that for any single instance of the aggregation

class PolicyActionInPolicyRule, this property (like all Reference

properties) is single-valued. The [0..n] cardinality indicates that

there may be 0, 1, or more than one PolicyRules that contain any

given PolicyAction.

7.8.2. The Reference "PartComponent"

This property is inherited from PolicyComponent, and overridden to

become an object reference to a PolicyAction contained by one or more

PolicyRules. Note that for any single instance of the aggregation

class PolicyActionInPolicyRule, this property (like all Reference

properties) is single-valued. The [0..n] cardinality indicates that

a given PolicyRule may contain 0, 1, or more than one PolicyActions.

7.8.3. The Property "ActionOrder"

This property provides an unsigned integer 'n' that indicates the

relative position of an action in the sequence of actions associated

with a policy rule. When 'n' is a positive integer, it indicates a

place in the sequence of actions to be performed, with smaller

integers indicating earlier positions in the sequence. The special

value '0' indicates "don't care". If two or more actions have the

same non-zero sequence number, they may be performed in any order,

but they must all be performed at the appropriate place in the

overall action sequence.

A series of examples will make ordering of actions clearer:

o If all actions have the same sequence number, regardless of

whether it is '0' or non-zero, any order is acceptable.

o The values

1:ACTION A

2:ACTION B

1:ACTION C

3:ACTION D

indicate two acceptable orders: A,C,B,D or C,A,B,D, since A and C

can be performed in either order, but only at the '1' position.

o The values

0:ACTION A

2:ACTION B

3:ACTION C

3:ACTION D

require that B,C, and D occur either as B,C,D or as B,D,C. Action

A may appear at any point relative to B,C, and D. Thus the

complete set of acceptable orders is: A,B,C,D; B,A,C,D; B,C,A,D;

B,C,D,A; A,B,D,C; B,A,D,C; B,D,A,C; B,D,C,A.

Note that the non-zero sequence numbers need not start with '1',

and they need not be consecutive. All that matters is their

relative magnitude.

The property is defined as follows:

NAME ActionOrder

DESCRIPTION Unsigned integer indicating the relative position

of an action in the sequence of actions aggregated

by a policy rule.

SYNTAX uint16

7.9. The Abstract Association "PolicyInSystem"

This abstract association inherits two object references from a

higher- level CIM association class, Dependency. It overrides these

object references to make them references to instances of the classes

System and Policy. Subclasses of PolicyInSystem then override these

object references again, to make them references to concrete policy

classes.

The value of the abstract superclass is to convey that all subclasses

have the same "dependency" semantics, and for ease of query to locate

all policy "dependencies" on a System. These dependencies are

related to scoping or hosting of the Policy.

The class definition for the association is as follows:

NAME PolicyInSystem

DESCRIPTION A generic association used to establish

dependency relationships between Policies and the

Systems that host them.

DERIVED FROM Dependency

ABSTRACT TRUE

PROPERTIES Antecedent[ref System[0..1]]

Dependent[ref Policy[0..n]]

7.10. The Weak Association "PolicyGroupInSystem"

This association links a PolicyGroup to the System in whose scope the

PolicyGroup is defined.

The class definition for the association is as follows:

NAME PolicyGroupInSystem

DESCRIPTION A class representing the fact that a PolicyGroup

is defined within the scope of a System.

DERIVED FROM PolicyInSystem

ABSTRACT FALSE

PROPERTIES Antecedent[ref System[1..1]]

Dependent[ref PolicyGroup[weak]]

7.10.1. The Reference "Antecedent"

This property is inherited from PolicyInSystem, and overridden to

restrict its cardinality to [1..1]. It serves as an object reference

to a System that provides a scope for one or more PolicyGroups.

Since this is a weak association, the cardinality for this object

reference is always 1, that is, a PolicyGroup is always defined

within the scope of exactly one System.

7.10.2. The Reference "Dependent"

This property is inherited from PolicyInSystem, and overridden to

become an object reference to a PolicyGroup defined within the scope

of a System. Note that for any single instance of the association

class PolicyGroupInSystem, this property (like all Reference

properties) is single-valued. The [0..n] cardinality indicates that

a given System may have 0, 1, or more than one PolicyGroups defined

within its scope.

7.11. The Weak Association "PolicyRuleInSystem"

Regardless of whether it belongs to a PolicyGroup (or to multiple

PolicyGroups), a PolicyRule is itself defined within the scope of a

System. This association links a PolicyRule to the System in whose

scope the PolicyRule is defined.

The class definition for the association is as follows:

NAME PolicyRuleInSystem

DESCRIPTION A class representing the fact that a PolicyRule

is defined within the scope of a System.

DERIVED FROM PolicyInSystem

ABSTRACT FALSE

PROPERTIES Antecedent[ref System[1..1]]

Dependent[ref PolicyRule[weak]]

7.11.1. The Reference "Antecedent"

This property is inherited from PolicyInSystem, and overridden to

restrict its cardinality to [1..1]. It serves as an object reference

to a System that provides a scope for one or more PolicyRules. Since

this is a weak association, the cardinality for this object reference

is always 1, that is, a PolicyRule is always defined within the scope

of exactly one System.

7.11.2. The Reference "Dependent"

This property is inherited from PolicyInSystem, and overridden to

become an object reference to a PolicyRule defined within the scope

of a System. Note that for any single instance of the association

class PolicyRuleInSystem, this property (like all Reference

properties) is single-valued. The [0..n] cardinality indicates that

a given System may have 0, 1, or more than one PolicyRules defined

within its scope.

7.12. The Association "PolicyConditionInPolicyRepository"

A reusable policy condition is always related to a single

PolicyRepository, via the PolicyConditionInPolicyRepository

association. This is not true for all PolicyConditions, however. An

instance of PolicyCondition that represents a rule-specific condition

is not related to any policy repository via this association.

The class definition for the association is as follows:

NAME PolicyConditionInPolicyRepository

DESCRIPTION A class representing the inclusion of a reusable

PolicyCondition in a PolicyRepository.

DERIVED FROM PolicyInSystem

ABSTRACT FALSE

PROPERTIES Antecedent[ref PolicyRepository[0..1]]

Dependent[ref PolicyCondition[0..n]]

7.12.1. The Reference "Antecedent"

This property is inherited from PolicyInSystem, and overridden to

become an object reference to a PolicyRepository containing one or

more PolicyConditions. A reusable PolicyCondition is always related

to exactly one PolicyRepository via the

PolicyConditionInPolicyRepository association. The [0..1]

cardinality for this property covers the two types of

PolicyConditions: 0 for a rule-specific PolicyCondition, 1 for a

reusable one.

7.12.2. The Reference "Dependent"

This property is inherited from PolicyInSystem, and overridden to

become an object reference to a PolicyCondition included in a

PolicyRepository. Note that for any single instance of the

association class PolicyConditionInPolicyRepository, this property

(like all Reference properties) is single-valued. The [0..n]

cardinality indicates that a given PolicyRepository may contain 0, 1,

or more than one PolicyConditions.

7.13. The Association "PolicyActionInPolicyRepository"

A reusable policy action is always related to a single

PolicyRepository, via the PolicyActionInPolicyRepository association.

This is not true for all PolicyActions, however. An instance of

PolicyAction that represents a rule-specific action is not related to

any policy repository via this association.

The class definition for the association is as follows:

NAME PolicyActionInPolicyRepository

DESCRIPTION A class representing the inclusion of a reusable

PolicyAction in a PolicyRepository.

DERIVED FROM PolicyInSystem

ABSTRACT FALSE

PROPERTIES Antecedent[ref PolicyRepository[0..1]]

Dependent[ref PolicyAction[0..n]]

7.13.1. The Reference "Antecedent"

This property is inherited from PolicyInSystem, and overridden to

become an object reference to a PolicyRepository containing one or

more PolicyActions. A reusable PolicyAction is always related to

exactly one PolicyRepository via the PolicyActionInPolicyRepository

association. The [0..1] cardinality for this property covers the two

types of PolicyActions: 0 for a rule-specific PolicyAction, 1 for a

reusable one.

7.13.2. The Reference "Dependent"

This property is inherited from PolicyInSystem, and overridden to

become an object reference to a PolicyAction included in a

PolicyRepository. Note that for any single instance of the

association class PolicyActionInPolicyRepository, this property (like

all Reference properties) is single-valued. The [0..n] cardinality

indicates that a given PolicyRepository may contain 0, 1, or more

than one PolicyActions.

7.14. The Aggregation "PolicyRepositoryInPolicyRepository"

The PolicyRepositoryInPolicyRepository aggregation enables policy

repositories to be nested. This derives from the higher level CIM

association, CIM_SystemComponent, describing that Systems contain

other ManagedSystemElements. This superclass could not be used for

the other Policy aggregations, since Policies are not

ManagedSystemElements, but ManagedElements. Note that it is assumed

that this aggregation is used to form directed acyclic graphs and NOT

ring structures.

The class definition for the aggregation is as follows:

NAME PolicyRepositoryInPolicyRepository

DESCRIPTION A class representing the aggregation of

PolicyRepositories by a higher-level

PolicyRepository.

DERIVED FROM SystemComponent

ABSTRACT FALSE

PROPERTIES GroupComponent[ref PolicyRepository[0..n]]

PartComponent[ref PolicyRepository[0..n]]

7.14.1. The Reference "GroupComponent"

This property is inherited from the CIM class SystemComponent, and

overridden to become an object reference to a PolicyRepository that

contains one or more other PolicyRepositories. Note that for any

single instance of the aggregation class

PolicyRepositoryInPolicyRepository, this property (like all Reference

properties) is single-valued. The [0..n] cardinality indicates that

there may be 0, 1, or more than one PolicyRepositories that contain

any given PolicyRepository.

7.14.2. The Reference "PartComponent"

This property is inherited from the CIM class SystemComponent, and

overridden to become an object reference to a PolicyRepository

contained by one or more other PolicyRepositories. Note that for any

single instance of the aggregation class

PolicyRepositoryInPolicyRepository, this property (like all Reference

properties) is single-valued. The [0..n] cardinality indicates that

a given PolicyRepository may contain 0, 1, or more than one other

PolicyRepositories.

8. Intellectual Property

The IETF takes no position regarding the validity or scope of any

intellectual property or other rights that might be claimed to

pertain to the implementation or use of the technology described in

this document or the extent to which any license under such rights

might or might not be available; neither does it represent that it

has made any effort to identify any such rights. Information on the

IETF's procedures with respect to rights in standards-track and

standards-related documentation can be found in BCP-11.

Copies of claims of rights made available for publication and any

assurances of licenses to be made available, or the result of an

attempt made to oBTain a general license or permission for the use of

such proprietary rights by implementers or users of this

specification can be obtained from the IETF Secretariat.

The IETF invites any interested party to bring to its attention any

copyrights, patents or patent applications, or other proprietary

rights which may cover technology that may be required to practice

this standard. Please address the information to the IETF Executive

Director.

9. Acknowledgements

The Policy Core Information Model in this document is closely based

on the work of the DMTF's Service Level Agreements working group, so

thanks are due to the members of that working group. Several of the

policy classes in this model first appeared in early drafts on IPSec

policy and QoS policy. The authors of these drafts were Partha

Bhattacharya, Rob Adams, William Dixon, Roy Pereira, Raju Rajan,

Jean-Christophe Martin, Sanjay Kamat, Michael See, Rajiv Chaudhury,

Dinesh Verma, George Powers, and Raj Yavatkar. Some other elements

of the model originated in work done by Yoram Snir, Yoram Ramberg,

and Ron Cohen. In addition, we would like to thank Harald Alvestrand

for conducting a thorough review of this document and providing many

helpful suggestions, and Luis Sanchez and Russ Mundy for their help

with the document's Security Considerations.

10. Security Considerations

The Policy Core Information Model (PCIM) presented in this document

provides an object-oriented model for describing policy information.

It provides a basic framework for describing the structure of policy

information, in a form independent of any specific repository or

access protocol, for use by an operational system. PCIM is not

intended to represent any particular system design or implementation,

nor does it define a protocol, and as such it does not have any

specific security requirements.

However, it should also be noted that certain derivative documents,

which use PCIM as a base, will need to convey more specific security

considerations. In order to communicate the nature of what will be

expected in these follow-on derivative documents, it is necessary to

review the reasons that PCIM, as defined in this document, is neither

implementable, nor representative of any real-world system, as well

as the nature of the expected follow-on extensions and mappings.

There are three independent reasons that PCIM, as defined here, is

neither implementable nor representative of any real-world system:

1. Its classes are independent of any specific repository that

uses any specific access protocol. Therefore, its classes are

designed not to be implemented directly. PCIM should instead

be viewed as a schematic that directs how information should be

represented, independent of any specific model implementation

constraints.

2. Its classes were designed to be independent of any specific

policy domain. For example, DiffServ and IPSec represent two

different policy domains. Each document which extends PCIM to

one of these domains will derive subclasses from the classes

and relationships defined in PCIM, in order to represent

extensions of a generic model to cover specific technical

domains.

3. It's an information model, which must be mapped to a specific

data model (native CIM schema, LDAP schema, MIB, whatever)

before it can be implemented. Derivative documents will map

the extended information models noted in item 2, above, to

specific types of data model implementations.

Even though specific security requirements are not appropriate for

PCIM, specific security requirements MUST be defined for each

operational real- world application of PCIM. Just as there will be a

wide range of operational, real-world systems using PCIM, there will

also be a wide range of security requirements for these systems.

Some operational, real-world systems that are deployed using PCIM may

have extensive security requirements that impact nearly all classes

and subclasses utilized by such a system, while other systems'

security requirements might have very little impact.

The derivative documents, discussed above, will create the context

for applying operational, real-world, system-level security

requirements against the various models which derive from PCIM.

For example, in some real-world scenarios, the values associated with

certain properties, within certain instantiated classes, may

represent information associated with scarce, and/or costly (and

therefore valuable) resources. It may be the case that these values

must not be disclosed to, or manipulated by, unauthorized parties.

As long as the derived model remains an information model (as opposed

to a data model), it is not possible to discuss the data model-

specific tools and mechanisms that are available for achieving the

authentication and authorization implicit in a requirement that

restricts read and/or read- write access to these values. Therefore,

these mechanisms will need to be discussed in each of the data models

to which the derived information models are mapped. If there are any

general security requirements that can be identified and can be

applied across multiple types of data models, it would be appropriate

to discuss those at the information model level, rather than the data

model level. In any case, any identified security requirements that

are not dealt with in the information model document, MUST be dealt

with in the derivative data model documents.

We can illustrate these points by extending the example from Section

2. A real-world system that provides QoS Gold Service to John would

likely need to provide at least the following security-related

capabilities and mechanisms (see [12] for definitions of security

related terms):

o Data integrity for the information (e.g., property values and

instantiated relationships) that specify that John gets QoS Gold

Service, from the point(s) that the information is entered into

the system to the point(s) where network components actually

provide that Service.

o Authentication and Authorization methods to ensure that only

system administrators (and not John or other engineers) can

remotely administer components of the system.

o An Authentication method to insure that John receives Gold

Service, and the other members of the engineering group receive

Bronze Service.

These are one possible set of requirements associated with an example

real-world system which delivers Gold Service, and the appropriate

place to document these would be in some combination of the

information model and the derivative data models for QoS Policy.

Each of the data models would also need to discuss how these

requirements are satisfied, using the mechanisms typically available

to such a data model, given the particular technology or set of

technologies which it may employ.

11. References

[1] Distributed Management Task Force, Inc., "DMTF Technologies: CIM

Standards << CIM Schema: Version 2.4", available via links on

the following DMTF web page:

http://www.dmtf.org/spec/cim_schema_v24.html.

[2] Distributed Management Task Force, Inc., "Common Information

Model (CIM) Specification, version 2.2, June 1999. This

document is available on the following DMTF web page:

http://www.dmtf.org/spec/cims.html.

[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement

Levels", BCP 14, RFC2119, March 1997.

[4] Hovey, R. and S. Bradner, "The Organizations Involved in the

IETF Standards Process", BCP 11, RFC2028, October 1996.

[5] J. Strassner and S. Judd, "Directory-Enabled Networks", version

3.0c5 (August 1998). A PDF file is available at

http://www.murchiso.com/den/#denspec.

[6] J. Strassner, policy architecture BOF presentation, 42nd IETF

Meeting, Chicago, Illinois, October, 1998. Minutes of this BOF

are available at the following location:

http://www.ietf.org/proceedings/98aug/index.html.

[7] Yergeau, F., "UTF-8, a transformation format of ISO 10646", RFC

2279, January 1998.

[8] Levi, D. and J. Schoenwaelder, "Definitions of Managed Objects

for Scheduling Management Operations", RFC2591, May 1999.

[9] Yavatkar, R., Pendarakis, D. and R. Guerin, "A Framework for

Policy-based Admission Control", RFC2753, January 2000.

[10] Dawson, F. and D. Stenerson, "Internet Calendaring and

Scheduling Core Object Specification (iCalendar)", RFC2445,

November 1998.

[11] Strassner, J., and E. Ellesson, B. Moore, R. Moats, "Policy Core

LDAP Schema", Work in Progress.

[12] Shirey, R., "Internet Security Glossary", FYI 36, RFC2828, May

2000.

Note: the CIM 2.4 Schema specification is defined by the following

set of MOF files, available from the following URL:

http://www.dmtf.org/spec/CIM_Schema24/CIM_Schema24.zip

12. Authors' Addresses

Ed Ellesson

LongBoard, Inc.

2505 Meridian Pkwy, #100

Durham, NC 27713

Phone: +1 919-361-3230

Fax: +1 919-361-3299

EMail: eellesson@lboard.com

Bob Moore

IBM Corporation, BRQA/502

4205 S. Miami Blvd.

Research Triangle Park, NC 27709

Phone: +1 919-254-4436

Fax: +1 919-254-6243

EMail: remoore@us.ibm.com

John Strassner

Cisco Systems, Bldg 15

170 West Tasman Drive

San Jose, CA 95134

Phone: +1 408-527-1069

Fax: +1 408-527-6351

EMail: johns@cisco.com

Andrea Westerinen

Cisco Systems

170 West Tasman Drive

San Jose, CA 95134

Phone: +1 408-853-8294

Fax: +1 408-527-6351

EMail: andreaw@cisco.com

13. Appendix A: Class Identification in a Native CIM Implementation

While the CommonName property is present in the abstract superclass

Policy, and is thus available in all of its instantiable subclasses,

CIM does not use this property for naming instances. The following

subsections discuss how naming is handled in a native CIM

implementation for each of the instantiable classes in the Policy

Core Information Model.

Two things should be noted regarding CIM naming:

o When a CIM association is specified as "weak", this is a statement

about naming scopes: an instance of the class at the weak end of

the association is named within the scope of an instance of the

class at the other end of the association. This is accomplished

by propagation of keys from the instance of the scoping class to

the instance of the weak class. Thus the weak class has, via key

propagation, all the keys from the scoping class, and it also has

one or more additional keys for distinguishing instances of the

weak class, within the context of the scoping class.

o All class names in CIM are limited to alphabetic and numeric

characters plus the underscore, with the restriction that the

first character cannot be numeric. Refer to Appendix F "Unicode

Usage" in reference [2] for an exact specification of how CIM

class names are encoded in CIM strings.

13.1. Naming Instances of PolicyGroup and PolicyRule

A policy group always exists in the context of a system. In the

Policy Core Information Model, this is captured by the weak

aggregation PolicyGroupInSystem between a PolicyGroup and a System.

Note that System serves as the base class for describing network

devices and administrative domains.

A policy rule also exists in the context of a system. In the Policy

Core Information Model, this is captured by the weak association

PolicyRuleInSystem between a PolicyRule and a System.

The following sections define the CIM keys for PolicyGroup and

PolicyRule.

13.1.1. PolicyGroup's CIM Keys

The CIM keys of the PolicyGroup class are:

o SystemCreationClassName (A CIM_System key, propagated due to the

weak association, PolicyGroupInSystem)

o SystemName (A CIM_System key, propagated due to the weak

association, PolicyGroupInSystem)

o CreationClassName

o PolicyGroupName

They are defined in Reference [1] as follows:

NAME SystemCreationClassName

DESCRIPTION SystemCreationClassName represents the class name of

the CIM System object providing the naming scope for

the instance of PolicyGroup.

SYNTAX string [MaxLen 256]

QUALIFIER key

NAME SystemName

DESCRIPTION SystemName represent the individual name of the

particular System object, providing the naming scope

for the instance of PolicyGroup.

SYNTAX string [MaxLen 256]

QUALIFIER key

NAME CreationClassName

DESCRIPTION This property is set to "CIM_PolicyGroup", if the

PolicyGroup object is directly instantiated. Or, it

is equal to the class name of the PolicyGroup

subclass that is instantiated.

SYNTAX string [MaxLen 256]

QUALIFIER key

NAME PolicyGroupName

DESCRIPTION The identifying name of this policy group.

SYNTAX string [MaxLen 256]

QUALIFIER key

13.1.2. PolicyRule's CIM Keys

The CIM keys of the PolicyRule class are:

o SystemCreationClassName (A CIM_System key, propagated due to the

weak association PolicyRuleInSystem)

o SystemName (A CIM_System key, propagated due to the weak

association PolicyRuleInSystem)

o CreationClassName

o PolicyRuleName

SystemCreationClassName and SystemName work the same as defined for

the class PolicyGroup. See Section 13.1.1 for details.

The other two properties are defined in Reference [1] as follows:

NAME CreationClassName

DESCRIPTION This property is set to "CIM_PolicyRule", if the

PolicyRule object is directly instantiated. Or,

it is equal to the class name of the PolicyRule

subclass that is instantiated.

SYNTAX string [MaxLen 256]

QUALIFIER key

NAME PolicyRuleName

DESCRIPTION The identifying name of this policy rule.

SYNTAX string [MaxLen 256]

QUALIFIER key

13.2. Naming Instances of PolicyCondition and Its Subclasses

The CIM keys of the PolicyCondition class are:

o SystemCreationClassName

o SystemName

o PolicyRuleCreationClassName

o PolicyRuleName

o CreationClassName

o PolicyConditionName

Note that none of the keys are defined as propagated, although they

appear to fit this convention. The reason for this difference is

because (as indicated in Sections 5.1 and 6.4) the PolicyCondition

class is used to represent both reusable and rule-specific

conditions. This, in turn, affects what associations are valid for

an instance of PolicyCondition, and how that instance is named.

In an ideal world, an instance of the PolicyCondition class would be

scoped either by its PolicyRepository (for a reusable condition) or

by its PolicyRule (for a rule-specific condition). However, CIM has

the restriction that a given class can only be "weak" to one other

class (i.e., defined by one weak association).

To work within the restrictions of CIM naming, it is necessary to

"simulate" weak associations between PolicyCondition and PolicyRule,

and between PolicyCondition and PolicyRepository, through a technique

we'll call manual key propagation. Strictly speaking, manual key

propagation isn't key propagation at all. But it has the same effect

as (true) key propagation, so the name fits.

Figure 9 illustrates how manual propagation works in the case of

PolicyCondition. (Note that only the key properties are shown for

each of the classes.) In the figure, the line composed of 'I's

indicates class inheritance, the one composed of 'P's indicates

(true) key propagation via the weak aggregation PolicyRuleInSystem,

and the ones composed of 'M's indicate manual key propagation.

+------------------+

System

+------------------+

CreationClassName

Name

+------------------+

^ P

I PPPPPPPPPPPPPPPPPPPPPPPPPPPP

I P

+------------------+ +---------------v--------------+

AdminDomain PolicyRule

+------------------+ +------------------------------+

CreationClassName System.CreationClassName

Name System.Name

+------------------+ CreationClassName

^ PolicyRuleName

I +------------------------------+

I M

I M

+------------------+ M

PolicyRepository M

+------------------+ M

CreationClassName M

Name M

+------------------+ M

M M

M M

M M

+----v-------------------v----+

PolicyCondition

+-----------------------------+

SystemCreationClassName

SystemName

PolicyRuleCreationClassName

PolicyRuleName

CreationClassName

PolicyConditionName

+-----------------------------+

Figure 9. Manual Key Propagation for Naming PolicyConditions

Looking at Figure 9, we see that two key properties,

CreationClassName and Name, are defined in the System class, and

inherited by its subclasses AdminDomain and PolicyRepository. Since

PolicyRule is weak to System, these two keys are propagated to it; it

also has its own keys CreationClassName and PolicyRuleName.

A similar approach, though not automatic, is used in "manual key

propagation". Here is the approach for rule-specific and reusable

PolicyConditions:

o The manual propagation of keys from PolicyRule to PolicyCondition

involves copying the values of PolicyRule's four key properties

into four similarly named key properties in PolicyCondition. From

the point of view of the CIM specification language, the property

SystemName in PolicyCondition is a completely new key property.

However, the relationship to the Name property in System is

defined in the description of SystemName.

o The manual propagation of keys from PolicyRepository to

PolicyCondition works in exactly the same way for the first two

key properties. However, since PolicyRepository doesn't include

PolicyRule properties, the PolicyRuleCreationClassName and

PolicyRuleName have no values. A special value, "No Rule", is

assigned to both of these properties in this case, indicating that

this instance of PolicyCondition is not named within the scope of

any particular policy rule.

The following section defines the specific CIM keys for

PolicyCondition.

13.2.1. PolicyCondition's CIM Keys

PolicyCondition's key properties are defined in Reference [1] as

follows:

NAME SystemCreationClassName

DESCRIPTION SystemCreationClassName represents the class

name of the CIM System object providing the

naming scope for the instance of PolicyCondition.

For a rule-specific policy condition, this is the

type of system (e.g., the name of the class that

created this instance) in whose context the policy

rule is defined. For a reusable policy condition,

this is set to "CIM_PolicyRepository", if the

PolicyRepository object is directly instantiated.

Or, it is equal to the class name of the

PolicyRepository subclass that is instantiated.

SYNTAX string [MaxLen 256]

QUALIFIER key

NAME SystemName

DESCRIPTION The name of the System object in whose scope this

policy condition is defined. This property

completes the identification of the System object.

For a rule-specific policy condition, this is the

name of the instance of the system in whose

context the policy rule is defined. For a

reusable policy condition, this is name of the

instance of PolicyRepository that holds the policy

condition.

SYNTAX string [MaxLen 256]

QUALIFIER key

NAME PolicyRuleCreationClassName

DESCRIPTION For a rule-specific policy condition, this

property identifies the class name of the policy

rule instance, in whose scope this instance of

PolicyCondition exists. For a reusable policy

condition, this property is set to a special

value, "No Rule", indicating that this instance

of PolicyCondition is not unique to one policy

rule.

SYNTAX string [MaxLen 256]

QUALIFIER key

NAME PolicyRuleName

DESCRIPTION For a rule-specific policy condition,

PolicyRuleName completes the identification of

the PolicyRule object with which this condition

is associated. For a reusable policy condition,

a special value, "No Rule", is used to indicate

that this condition is reusable.

SYNTAX string [MaxLen 256]

QUALIFIER key

NAME CreationClassName

DESCRIPTION The class name of the PolicyCondition subclass

that is instantiated.

SYNTAX string [MaxLen 256]

QUALIFIER key

NAME PolicyConditionName

DESCRIPTION The identifying name of this policy condition.

SYNTAX string [MaxLen 256]

QUALIFIER key

13.3. Naming Instances of PolicyAction and Its Subclasses

From the point of view of naming, the PolicyAction class and its

subclasses work exactly like the PolicyCondition class and its

subclasses. See Section 13.2 and 13.2.1 for details.

Specifically, the CIM keys of PolicyAction are:

o SystemCreationClassName

o SystemName

o PolicyRuleCreationClassName

o PolicyRuleName

o CreationClassName

o PolicyActionName

They are defined in Reference [1] as follows:

NAME SystemCreationClassName

DESCRIPTION SystemCreationClassName represents the class name

of the CIM System object providing the naming

scope for the instance of PolicyAction. For a

rule-specific policy action, this is the type of

system (e.g., the name of the class that created

this instance) in whose context the policy rule

is defined. For a reusable policy action, this

is set to "CIM_PolicyRepository", if the

PolicyRepository object is directly instantiated.

Or, it is equal to the class name of the

PolicyRepository subclass that is instantiated.

SYNTAX string [MaxLen 256]

QUALIFIER key

NAME SystemName

DESCRIPTION The name of the System object in whose scope this

policy action is defined. This property completes

the identification of the System object. For a

rule-specific policy action, this is the name of

the instance of the system in whose context the

policy rule is defined. For a reusable policy

action, this is name of the instance of

PolicyRepository that holds the policy action.

SYNTAX string [MaxLen 256]

QUALIFIER key

NAME PolicyRuleCreationClassName

DESCRIPTION For a rule-specific policy action, this property

identifies the class name of the policy rule

instance, in whose scope this instance of

PolicyAction exists. For a reusable policy

action, this property is set to a special value,

"No Rule", indicating that this instance of

PolicyAction is not unique to one policy rule.

SYNTAX string [MaxLen 256]

QUALIFIER key

NAME PolicyRuleName

DESCRIPTION For a rule-specific policy action, PolicyRuleName

completes the identification of the PolicyRule

object with which this action is associated. For

a reusable policy action, a special value, "No

Rule", is used to indicate that this action is

reusable.

SYNTAX string [MaxLen 256]

QUALIFIER key

NAME CreationClassName

DESCRIPTION The class name of the PolicyAction subclass that is

instantiated.

SYNTAX string [MaxLen 256]

QUALIFIER key

NAME PolicyActionName

DESCRIPTION The identifying name of this policy action.

SYNTAX string [MaxLen 256]

QUALIFIER key

13.4. Naming Instances of PolicyRepository

An instance of PolicyRepository is named by the two key properties

CreationClassName and Name that it inherits from its superclass

AdminDomain. These properties are actually defined in AdminDomain's

superclass, System, and then inherited by AdminDomain.

For instances of PolicyRepository itself, the value of

CreationClassName must be "CIM_PolicyRepository". (Recall that for

readability the prefix "CIM_" has been omitted from all class names

in this document). If a subclass of PolicyRepository (perhaps

QosPolicyRepository) is defined and instantiated, then the class name

"CIM_QosPolicyRepository" is used in CreationClassName.

The Name property simply completes the identification of the instance

of PolicyRepository.

13.5. Role of the CreationClassName Property in Naming

To provide for more flexibility in instance naming, CIM makes use of

a property called CreationClassName. The idea of CreationClassName

is to provide another dimension that can be used to avoid naming

collisions, in the specific case of instances belonging to two

different subclasses of a common superclass. An example will

illustrate how CreationClassName works.

Suppose we have instances of two different subclasses of

PolicyCondition, FrameRelayPolicyCondition and BgpPolicyCondition,

and that these instances apply to the same context. If we had only

the single key property PolicyConditionName available for

distinguishing the two instances, then a collision would result from

naming both of the instances with the key value PCName = "PC-1".

Thus policy administrators from widely different disciplines would

have to coordinate their naming of PolicyConditions for this context.

With CreationClassName, collisions of this type can be eliminated,

without requiring coordination among the policy administrators. The

two instances can be distinguished by giving their CreationClassNames

different values. One instance is now identified with the two keys

CreationClassName = "FrameRelayPolicyCondition" + PCName = "PC-1",

while the other is identified with

CreationClassName = "BgpPolicyCondition" + PCName = "PC-1".

Each of the instantiable classes in the Core Model includes the

CreationClassName property as a key in addition to its own class-

specific key property.

13.6. Object References

Today, all CIM associations involve two object references. CIM

decomposes an object reference into two parts: a high-order part

that identifies an object manager and namespace, and a model path

that identifies an object instance within a namespace. The model

path, in turn, can be decomposed into an object class identifier and

a set of key values needed to identify an instance of that class.

Because the object class identifier is part of the model path, a CIM

object reference is strongly typed. The GroupComponent object

reference in the PolicyGroupInPolicyGroup association, for example,

can only point to an instance of PolicyGroup, or to an instance of a

subclass of PolicyGroup. Contrast this with LDAP, where a DN pointer

is completely untyped: it identifies (by DN) an entry, but places no

restriction on that entry's object class(es).

An important difference between CIM property definitions and LDAP

attribute type definitions was identified earlier in Section 6:

while an LDAP attribute type definition has global scope, a CIM

property definition applies only to the class in which it is defined.

Thus properties having the same name in two different classes are

free to have different data types. CIM takes advantage of this

flexibility by allowing the data type of an object reference to be

overridden in a subclass of the association class in which it was

initially defined.

For example, the object reference GroupComponent is defined in the

abstract aggregation class PolicyComponent to be a reference to an

instance of the class Policy. This data type for GroupComponent is

then overridden in subclasses of PolicyComponent. In

PolicyGroupInPolicyGroup, for example, GroupComponent becomes a

reference to an instance of PolicyGroup. But in

PolicyConditionInPolicyRule it becomes a reference to an instance of

PolicyRule. Of course there is not total freedom in this overriding

of object references. In order to remain consistent with its

abstract superclass, a subclass of PolicyComponent can only override

GroupComponent to be a reference to a subclass of Policy. A Policy

class is the generic context for the GroupComponent reference in

PolicyComponent.

14. Appendix B: The Core Policy MOF

// ==================================================================

// Title: Core Policy MOF Specification 2.4

// Filename: CIM_Policy24.MOF

// Version: 2.4

// Release: 0

// Description: The object classes below are listed in an order that

// avoids forward references. Required objects, defined

// by other working groups, are omitted.

// Date: 06/27/2000

// CIMCR516a - Rooted the model associations under Policy

// Component or PolicyInSystem. Corrected PolicyCondition/

// PolicyActionInPolicyRepository to subclass from

// PolicyInSystem (similar to Groups and Roles 'InSystem')

// ==================================================================

// Author: DMTF SLA (Service Level Agreement) Working Group

// ==================================================================

// Pragmas

// ==================================================================

#pragma Locale ("en-US")

// ==================================================================

// Policy

// ==================================================================

[Abstract, Description (

"An abstract class describing common properties of all "

"policy rule-related subclasses, such as PolicyGroup, Policy"

"Rule and PolicyCondition. All instances of policy rule-"

"related entities will be created from subclasses of CIM_"

"Policy. The exception to this statement is PolicyRepository "

"which is a type of CIM_System.")

]

class CIM_Policy : CIM_ManagedElement

{

[Description (

"A user-friendly name of this policy-related object.")

]

string CommonName;

[Description (

"An array of keywords for characterizing / categorizing "

"policy objects. Keywords are of one of two types: \n"

" o Keywords defined in this and other MOFs, or in DMTF "

" white papers. These keywords provide a vendor-"

" independent, installation-independent way of "

" characterizing policy objects. \n"

" o Installation-dependent keywords for characterizing "

" policy objects. Examples include 'Engineering', "

" 'Billing', and 'Review in December 2000'. \n"

"This MOF defines the following keywords: 'UNKNOWN', "

"'CONFIGURATION', 'USAGE', 'SECURITY', 'SERVICE', "

"'MOTIVATIONAL', 'INSTALLATION', and 'EVENT'. These "

"concepts are self-explanatory and are further discussed "

"in the SLA/Policy White Paper. One additional keyword "

"is defined: 'POLICY'. The role of this keyword is to "

"identify policy-related instances that may not be otherwise "

"identifiable, in some implementations. The keyword 'POLICY' "

"is NOT mutually exclusive of the other keywords "

"specified above.")

]

string PolicyKeywords [];

};

// ==================================================================

// PolicyComponent

// ==================================================================

[Association, Abstract, Aggregation, Description (

"CIM_PolicyComponent is a generic association used to "

"establish 'part of' relationships between the subclasses of "

"CIM_Policy. For example, the PolicyConditionInPolicyRule "

"association defines that PolicyConditions are part of a "

"PolicyRule.")

]

class CIM_PolicyComponent

{

[Aggregate, Key, Description (

"The parent Policy in the association.")

]

CIM_Policy REF GroupComponent;

[Key, Description (

"The child/part Policy in the association.")

]

CIM_Policy REF PartComponent;

};

// ==================================================================

// PolicyInSystem

// ==================================================================

[Association, Abstract, Description (

" CIM_PolicyInSystem is a generic association used to "

"establish dependency relationships between Policies and the "

"Systems that host them. These Systems may be ComputerSystems "

"where Policies are 'running' or they may be Policy"

"Repositories where Policies are stored. This relationship "

"is similar to the concept of CIM_Services being dependent "

"on CIM_Systems as defined by the HostedService "

"association. \n"

" Cardinality is Max(1) for the Antecedent/System "

"reference since Policies can only be hosted in at most one "

"System context. Some subclasses of the association will "

"further refine this definition to make the Policies Weak "

"to Systems. Other subclasses of PolicyInSystem will "

"define an optional hosting relationship. Examples of each "

"of these are the PolicyRuleInSystem and PolicyConditionIn"

"PolicyRepository associations, respectively.")

]

class CIM_PolicyInSystem : CIM_Dependency

{

[Override ("Antecedent"), Max (1), Description (

"The hosting System.")

]

CIM_System REF Antecedent;

[Override ("Dependent"), Description (

"The hosted Policy.")

]

CIM_Policy REF Dependent;

};

// ==================================================================

// PolicyGroup

// ==================================================================

[Description (

"A container for either a set of related PolicyGroups "

"or a set of related PolicyRules, but not both. Policy"

"Groups are defined and named relative to the CIM_System "

"which provides their context.")

]

class CIM_PolicyGroup : CIM_Policy

{

[Propagated("CIM_System.CreationClassName"),

Key, MaxLen (256),

Description ("The scoping System's CreationClassName.")

]

string SystemCreationClassName;

[Propagated("CIM_System.Name"),

Key, MaxLen (256),

Description ("The scoping System's Name.")

]

string SystemName;

[Key, MaxLen (256), Description (

"CreationClassName indicates the name of the class or the "

"subclass used in the creation of an instance. When used "

"with the other key properties of this class, this property "

"allows all instances of this class and its subclasses to "

"be uniquely identified.") ]

string CreationClassName;

[Key, MaxLen (256), Description (

"A user-friendly name of this PolicyGroup.")

]

string PolicyGroupName;

};

// ==================================================================

// PolicyGroupInPolicyGroup

// ==================================================================

[Association, Aggregation, Description (

"A relationship that aggregates one or more lower-level "

"PolicyGroups into a higher-level Group. A Policy"

"Group may aggregate either PolicyRules or other Policy"

"Groups, but not both.")

]

class CIM_PolicyGroupInPolicyGroup : CIM_PolicyComponent

{

[Override ("GroupComponent"), Aggregate, Description (

"A PolicyGroup that aggregates other Groups.")

]

CIM_PolicyGroup REF GroupComponent;

[Override ("PartComponent"), Description (

"A PolicyGroup aggregated by another Group.")

]

CIM_PolicyGroup REF PartComponent;

};

// ==================================================================

// PolicyGroupInSystem

// ==================================================================

[Association, Description (

"An association that links a PolicyGroup to the System "

"in whose scope the Group is defined.")

]

class CIM_PolicyGroupInSystem : CIM_PolicyInSystem

{

[Override ("Antecedent"), Min(1), Max(1), Description (

"The System in whose scope a PolicyGroup is defined.")

]

CIM_System REF Antecedent;

[Override ("Dependent"), Weak, Description (

"A PolicyGroup named within the scope of a System.")

]

CIM_PolicyGroup REF Dependent;

};

// ==================================================================

// PolicyRule

// ==================================================================

[Description (

" The central class for representing the 'If Condition then "

"Action' semantics associated with a policy rule. "

"A PolicyRule condition, in the most general sense, is "

"represented as either an ORed set of ANDed conditions "

"(Disjunctive Normal Form, or DNF) or an ANDed set of ORed "

"conditions (Conjunctive Normal Form, or CNF). Individual "

"conditions may either be negated (NOT C) or unnegated (C). "

"The actions specified by a PolicyRule are to be performed "

"if and only if the PolicyRule condition (whether it is "

"represented in DNF or CNF) evaluates to TRUE.\n\n"

" "

"The conditions and actions associated with a PolicyRule "

"are modeled, respectively, with subclasses of Policy"

"Condition and PolicyAction. These condition and action "

"objects are tied to instances of PolicyRule by the Policy"

"ConditionInPolicyRule and PolicyActionInPolicyRule "

"aggregations.\n\n"

" "

"A PolicyRule may also be associated with one or more policy "

"time periods, indicating the schedule according to which the "

"policy rule is active and inactive. In this case it is the "

"PolicyRuleValidityPeriod aggregation that provides this "

"linkage.\n\n"

" "

"The PolicyRule class uses the property ConditionListType, to "

"indicate whether the conditions for the rule are in DNF or "

"CNF. The PolicyConditionInPolicyRule aggregation contains "

"two additional properties to complete the representation of "

"the Rule's conditional expression. The first of these "

"properties is an integer to partition the referenced "

"PolicyConditions into one or more groups, and the second is a "

"Boolean to indicate whether a referenced Condition is "

"negated. An example shows how ConditionListType and these "

"two additional properties provide a unique representation "

"of a set of PolicyConditions in either DNF or CNF.\n\n"

" "

"Suppose we have a PolicyRule that aggregates five "

"PolicyConditions C1 through C5, with the following values "

"in the properties of the five PolicyConditionInPolicyRule "

"associations:\n"

" C1: GroupNumber = 1, ConditionNegated = FALSE\n "

" C2: GroupNumber = 1, ConditionNegated = TRUE\n "

" C3: GroupNumber = 1, ConditionNegated = FALSE\n "

" C4: GroupNumber = 2, ConditionNegated = FALSE\n "

" C5: GroupNumber = 2, ConditionNegated = FALSE\n\n "

" "

"If ConditionListType = DNF, then the overall condition for "

"the PolicyRule is:\n"

" (C1 AND (NOT C2) AND C3) OR (C4 AND C5)\n\n"

" "

"On the other hand, if ConditionListType = CNF, then the "

"overall condition for the PolicyRule is:\n"

" (C1 OR (NOT C2) OR C3) AND (C4 OR C5)\n\n"

" "

"In both cases, there is an unambiguous specification of "

"the overall condition that is tested to determine whether "

"to perform the PolicyActions associated with the PolicyRule.")

]

class CIM_PolicyRule : CIM_Policy

{

[Propagated("CIM_System.CreationClassName"),

Key, MaxLen (256),

Description ("The scoping System's CreationClassName.")

]

string SystemCreationClassName;

[Propagated("CIM_System.Name"),

Key, MaxLen (256),

Description ("The scoping System's Name.")

]

string SystemName;

[Key, MaxLen (256), Description (

"CreationClassName indicates the name of the class or the "

"subclass used in the creation of an instance. When used "

"with the other key properties of this class, this property "

"allows all instances of this class and its subclasses to "

"be uniquely identified.") ]

string CreationClassName;

[Key, MaxLen (256), Description (

"A user-friendly name of this PolicyRule.")

]

string PolicyRuleName;

[Description (

"Indicates whether this PolicyRule is administratively "

"enabled, administratively disabled, or enabled for "

"debug. When the property has the value 3 (\"enabledFor"

"Debug\"), the entity evaluating the PolicyConditions is "

"instructed to evaluate the conditions for the Rule, but not "

"to perform the actions if the PolicyConditions evaluate to "

"TRUE. This serves as a debug vehicle when attempting to "

"determine what policies would execute in a particular "

"scenario, without taking any actions to change state "

"during the debugging. The default value is 1

(\"enabled\")."),

ValueMap { "1", "2", "3" },

Values { "enabled", "disabled", "enabledForDebug" }

]

uint16 Enabled;

[Description (

"Indicates whether the list of PolicyConditions "

"associated with this PolicyRule is in disjunctive "

"normal form (DNF) or conjunctive normal form (CNF)."

"The default value is 1 (\"DNF\")."),

ValueMap { "1", "2" },

Values { "DNF", "CNF" }

]

uint16 ConditionListType;

[Description (

"A free-form string that can be used to provide "

"guidelines on how this PolicyRule should be used.")

]

string RuleUsage;

[Description (

"A non-negative integer for prioritizing this Policy"

"Rule relative to other Rules. A larger value "

"indicates a higher priority. The default value is 0.")

]

uint16 Priority;

[Description (

"A flag indicating that the evaluation of the Policy"

"Conditions and execution of PolicyActions (if the "

"Conditions evaluate to TRUE) is required. The "

"evaluation of a PolicyRule MUST be attempted if the "

"Mandatory property value is TRUE. If the Mandatory "

"property is FALSE, then the evaluation of the Rule "

"is 'best effort' and MAY be ignored.")

]

boolean Mandatory;

[Description (

"This property gives a policy administrator a way "

"of specifying how the ordering of the PolicyActions "

"associated with this PolicyRule is to be interpreted. "

"Three values are supported:\n"

" o mandatory(1): Do the actions in the indicated "

" order, or don't do them at all.\n"

" o recommended(2): Do the actions in the indicated "

" order if you can, but if you can't do them in this "

" order, do them in another order if you can.\n"

" o dontCare(3): Do them -- I don't care about the "

" order.\n"

"The default value is 3 (\"dontCare\")."),

ValueMap { "1", "2", "3" },

Values { "mandatory", "recommended", "dontCare" }

]

uint16 SequencedActions;

[Description (

"This property represents the roles and role combinations "

"associated with a PolicyRule. Each value represents one "

"role or role combination. Since this is a multi-valued "

"property, more than one role or combination can be associated "

"with a single policy rule. Each value is a string of the "

"form:\n"

" <RoleName>[&&<RoleName>]*\n"

"where the individual role names appear in alphabetical order "

"(according to the collating sequence for UCS-2).")

]

string PolicyRoles [];

};

// ==================================================================

// PolicyRuleInPolicyGroup

// ==================================================================

[Association, Aggregation, Description (

"A relationship that aggregates one or more PolicyRules "

"into a PolicyGroup. A PolicyGroup may aggregate either "

"PolicyRules or other PolicyGroups, but not both.")

]

class CIM_PolicyRuleInPolicyGroup : CIM_PolicyComponent

{

[Override ("GroupComponent"), Aggregate, Description (

"A PolicyGroup that aggregates one or more PolicyRules.")

]

CIM_PolicyGroup REF GroupComponent;

[Override ("PartComponent"), Description (

"A PolicyRule aggregated by a PolicyGroup.")

]

CIM_PolicyRule REF PartComponent;

};

// ==================================================================

// PolicyRuleInSystem

// ==================================================================

[Association, Description (

"An association that links a PolicyRule to the System "

"in whose scope the Rule is defined.")

]

class CIM_PolicyRuleInSystem : CIM_PolicyInSystem

{

[Override ("Antecedent"), Min(1), Max(1), Description (

"The System in whose scope a PolicyRule is defined.")

]

CIM_System REF Antecedent;

[Override ("Dependent"), Weak, Description (

"A PolicyRule named within the scope of a System.")

]

CIM_PolicyRule REF Dependent;

};

// ==================================================================

// PolicyRepository

// ==================================================================

[Description (

"A class representing an administratively defined "

"container for reusable policy-related information. "

"This class does not introduce any additional "

"properties beyond those in its superclass "

"AdminDomain. It does, however, participate in a "

"number of unique associations."

"\n\n"

"An instance of this class uses the NameFormat value"

"\"PolicyRepository\", which is defined in the AdminDomain"

"class.")

]

class CIM_PolicyRepository : CIM_AdminDomain

{

};

// ==================================================================

// PolicyRepositoryInPolicyRepository

// ==================================================================

[Association, Aggregation, Description (

"A relationship that aggregates one or more lower-level "

"PolicyRepositories into a higher-level Repository.")

]

class CIM_PolicyRepositoryInPolicyRepository : CIM_SystemComponent

{

[Override ("GroupComponent"), Aggregate, Description (

"A PolicyRepository that aggregates other Repositories.")

]

CIM_PolicyRepository REF GroupComponent;

[Override ("PartComponent"), Description (

"A PolicyRepository aggregated by another Repository.")

]

CIM_PolicyRepository REF PartComponent;

};

// ==================================================================

// PolicyCondition

// ==================================================================

[Abstract, Description (

"A class representing a rule-specific or reusable policy "

"condition to be evaluated in conjunction with a Policy"

"Rule. Since all operational details of a PolicyCondition "

"are provided in subclasses of this object, this class is "

"abstract.")

]

class CIM_PolicyCondition : CIM_Policy

{

[Key, MaxLen (256), Description (

" The name of the class or the subclass used in the "

"creation of the System object in whose scope this "

"PolicyCondition is defined.\n\n"

" "

"This property helps to identify the System object in "

"whose scope this instance of PolicyCondition exists. "

"For a rule-specific PolicyCondition, this is the System "

"in whose context the PolicyRule is defined. For a "

"reusable PolicyCondition, this is the instance of "

"PolicyRepository (which is a subclass of System) that "

"holds the Condition.\n\n"

" "

"Note that this property, and the analogous property "

"SystemName, do not represent propagated keys from an "

"instance of the class System. Instead, they are "

"properties defined in the context of this class, which "

"repeat the values from the instance of System to which "

"this PolicyCondition is related, either directly via the "

"PolicyConditionInPolicyRepository aggregation or indirectly "

"via the PolicyConditionInPolicyRule aggregation.")

]

string SystemCreationClassName;

[Key, MaxLen (256), Description (

" The name of the System object in whose scope this "

"PolicyCondition is defined.\n\n"

" "

"This property completes the identification of the System "

"object in whose scope this instance of PolicyCondition "

"exists. For a rule-specific PolicyCondition, this is the "

"System in whose context the PolicyRule is defined. For a "

"reusable PolicyCondition, this is the instance of "

"PolicyRepository (which is a subclass of System) that "

"holds the Condition.")

]

string SystemName;

[Key, MaxLen (256), Description (

"For a rule-specific PolicyCondition, the "

"CreationClassName of the PolicyRule object with which "

"this Condition is associated. For a reusable Policy"

"Condition, a special value, 'NO RULE', should be used to "

"indicate that this Condition is reusable and not "

"associated with a single PolicyRule.")

]

string PolicyRuleCreationClassName;

[Key, MaxLen (256), Description (

"For a rule-specific PolicyCondition, the name of "

"the PolicyRule object with which this Condition is "

"associated. For a reusable PolicyCondition, a "

"special value, 'NO RULE', should be used to indicate "

"that this Condition is reusable and not associated "

"with a single PolicyRule.")

]

string PolicyRuleName;

[Key, MaxLen (256), Description (

"CreationClassName indicates the name of the class or the "

"subclass used in the creation of an instance. When used "

"with the other key properties of this class, this property "

"allows all instances of this class and its subclasses to "

"be uniquely identified.") ]

string CreationClassName;

[Key, MaxLen (256), Description (

"A user-friendly name of this PolicyCondition.")

]

string PolicyConditionName;

};

// ==================================================================

// PolicyConditionInPolicyRule

// ==================================================================

[Association, Aggregation, Description (

" A PolicyRule aggregates zero or more instances of the "

"PolicyCondition class, via the PolicyConditionInPolicyRule "

"association. A Rule that aggregates zero Conditions is not "

"valid -- it may, however, be in the process of being entered "

"into a PolicyRepository or being defined for a System. Note "

"that a PolicyRule should have no effect until it is valid.\n\n"

" "

"The Conditions aggregated by a PolicyRule are grouped into "

"two levels of lists: either an ORed set of ANDed sets of "

"conditions (DNF, the default) or an ANDed set of ORed sets "

"of conditions (CNF). Individual PolicyConditions in these "

"lists may be negated. The property ConditionListType "

"specifies which of these two grouping schemes applies to a "

"particular PolicyRule.\n\n"

" "

"In either case, PolicyConditions are used to determine whether "

"to perform the PolicyActions associated with the

PolicyRule.\n\n"

" "

"One or more PolicyTimePeriodConditions may be among the "

"conditions associated with a PolicyRule via the Policy"

"ConditionInPolicyRule association. In this case, the time "

"periods are simply additional Conditions to be evaluated "

"along with any others that are specified for the Rule. ")

]

class CIM_PolicyConditionInPolicyRule : CIM_PolicyComponent

{

[Override ("GroupComponent"), Aggregate, Description (

"This property represents the PolicyRule that "

"contains one or more PolicyConditions.")

]

CIM_PolicyRule REF GroupComponent;

[Override ("PartComponent"), Description (

"This property holds the name of a PolicyCondition "

"contained by one or more PolicyRules.")

]

CIM_PolicyCondition REF PartComponent;

[Description (

"Unsigned integer indicating the group to which the "

"PolicyCondition identified by the ContainedCondition "

"property belongs. This integer segments the Conditions "

"into the ANDed sets (when the ConditionListType is "

"\"DNF\") or similarly the ORed sets (when the Condition"

"ListType is \"CNF\") that are then evaluated.")

]

uint16 GroupNumber;

[Description (

"Indication of whether the Condition identified by "

"the ContainedCondition property is negated. TRUE "

"indicates that the PolicyCondition IS negated, FALSE "

"indicates that it IS NOT negated.")

]

boolean ConditionNegated;

};

// ==================================================================

// PolicyConditionInPolicyRepository

// ==================================================================

[Association, Description (

" A class representing the hosting of reusable "

"PolicyConditions by a PolicyRepository. A reusable Policy"

"Condition is always related to a single PolicyRepository, "

"via this aggregation.\n\n"

" "

"Note, that an instance of PolicyCondition can be either "

"reusable or rule-specific. When the Condition is rule-"

"specific, it shall not be related to any "

"PolicyRepository via the PolicyConditionInPolicyRepository "

"aggregation.")

]

class CIM_PolicyConditionInPolicyRepository : CIM_PolicyInSystem

{

[Override ("Antecedent"), Max(1), Description (

"This property identifies a PolicyRepository "

"hosting one or more PolicyConditions. A reusable "

"PolicyCondition is always related to exactly one "

"PolicyRepository via the PolicyConditionInPolicyRepository "

"aggregation. The [0..1] cardinality for this property "

"covers the two types of PolicyConditions: 0 for a "

"rule-specific PolicyCondition, 1 for a reusable one.")

]

CIM_PolicyRepository REF Antecedent;

[Override ("Dependent"), Description (

"This property holds the name of a PolicyCondition"

"hosted in the PolicyRepository. ")

]

CIM_PolicyCondition REF Dependent;

};

// ==================================================================

// PolicyTimePeriodCondition

// ==================================================================

[Description (

" This class provides a means of representing the time "

"periods during which a PolicyRule is valid, i.e., active. "

"At all times that fall outside these time periods, the "

"PolicyRule has no effect. A Rule is treated as valid "

"at ALL times, if it does not specify a "

"PolicyTimePeriodCondition.\n\n"

" "

"In some cases a Policy Consumer may need to perform "

"certain setup / cleanup actions when a PolicyRule becomes "

"active / inactive. For example, sessions that were "

"established while a Rule was active might need to "

"be taken down when the Rule becomes inactive. In other "

"cases, however, such sessions might be left up. In this "

"case, the effect of deactivating the PolicyRule would "

"just be to prevent the establishment of new sessions. \n\n"

" "

"Setup / cleanup behaviors on validity period "

"transitions are not currently addressed by the Policy "

"Model, and must be specified in 'guideline' documents or "

"via subclasses of CIM_PolicyRule, CIM_PolicyTimePeriod"

"Condition or other concrete subclasses of CIM_Policy. If "

"such behaviors need to be under the control of the policy "

"administrator, then a mechanism to allow this control "

"must also be specified in the subclasses.\n\n"

" "

"PolicyTimePeriodCondition is defined as a subclass of "

"PolicyCondition. This is to allow the inclusion of "

"time-based criteria in the AND/OR condition definitions "

"for a PolicyRule.\n\n"

" "

"Instances of this class may have up to five properties "

"identifying time periods at different levels. The values "

"of all the properties present in an instance are ANDed "

"together to determine the validity period(s) for the "

"instance. For example, an instance with an overall "

"validity range of January 1, 2000 through December 31, "

"2000; a month mask that selects March and April; a "

"day-of-the-week mask that selects Fridays; and a time "

"of day range of 0800 through 1600 would be represented "

"using the following time periods:\n"

" Friday, March 5, 2000, from 0800 through 1600;\n "

" Friday, March 12, 2000, from 0800 through 1600;\n "

" Friday, March 19, 2000, from 0800 through 1600;\n "

" Friday, March 26, 2000, from 0800 through 1600;\n "

" Friday, April 2, 2000, from 0800 through 1600;\n "

" Friday, April 9, 2000, from 0800 through 1600;\n "

" Friday, April 16, 2000, from 0800 through 1600;\n "

" Friday, April 23, 2000, from 0800 through 1600;\n "

" Friday, April 30, 2000, from 0800 through 1600.\n\n"

" "

"Properties not present in an instance of "

"PolicyTimePeriodCondition are implicitly treated as having "

"their value 'always enabled'. Thus, in the example above, "

"the day-of-the-month mask is not present, and so the "

"validity period for the instance implicitly includes a "

"day-of-the-month mask that selects all days of the month. "

"If this 'missing property' rule is applied to its fullest, we "

"see that there is a second way to indicate that a Policy"

"Rule is always enabled: associate with it an instance of "

"PolicyTimePeriodCondition whose only properties with "

"specific values are its key properties.")

]

class CIM_PolicyTimePeriodCondition : CIM_PolicyCondition

{

[Description (

" This property identifies an overall range of calendar "

"dates and times over which a PolicyRule is valid. It is "

"formatted as a string representing a start date and time, "

"in which the character 'T' indicates the beginning of the "

"time portion, followed by the solidus character '/', "

"followed by a similar string representing an end date and "

"time. The first date indicates the beginning of the range, "

"while the second date indicates the end. Thus, the second "

"date and time must be later than the first. Date/times are "

"expressed as substrings of the form yyyymmddThhmmss. For "

"example: \n"

" 20000101T080000/20000131T120000 defines \n"

" January 1, 2000, 0800 through January 31, 2000, noon\n\n"

" "

"There are also two special cases in which one of the "

"date/time strings is replaced with a special string defined "

"in RFC2445.\n "

" o If the first date/time is replaced with the string "

" 'THISANDPRIOR', then the property indicates that a "

" PolicyRule is valid [from now] until the date/time "

" that appears after the '/'.\n"

" o If the second date/time is replaced with the string "

" 'THISANDFUTURE', then the property indicates that a "

" PolicyRule becomes valid on the date/time that "

" appears before the '/', and remains valid from that "

" point on. "),

ModelCorrespondence {

"CIM_PolicyTimePeriodCondition.MonthOfYearMask",

"CIM_PolicyTimePeriodCondition.DayOfMonthMask",

"CIM_PolicyTimePeriodCondition.DayOfWeekMask",

"CIM_PolicyTimePeriodCondition.TimeOfDayMask",

"CIM_PolicyTimePeriodCondition.LocalOrUtcTime"}

]

string TimePeriod;

[Octetstring, Description (

" The purpose of this property is to refine the valid time "

"period that is defined by the TimePeriod property, by "

"explicitly specifying in which months the PolicyRule is "

"valid. These properties work together, with the "

"TimePeriod used to specify the overall time period in "

"which the PolicyRule is valid, and the MonthOfYearMask used "

"to pick out the months during which the Rule is valid.\n\n"

" "

"This property is formatted as an octet string, structured "

"as follows:\n"

" o a 4-octet length field, indicating the length of the "

" entire octet string; this field is always set to "

" 0x00000006 for this property;\n"

" o a 2-octet field consisting of 12 bits identifying the "

" 12 months of the year, beginning with January and "

" ending with December, followed by 4 bits that are "

" always set to '0'. For each month, the value '1' "

" indicates that the policy is valid for that month, "

" and the value '0' indicates that it is not valid.\n\n"

" "

"The value 0x000000060830, for example, indicates that a "

"PolicyRule is valid only in the months May, November, "

"and December.\n\n"

" "

"If a value for this property is not provided, then the "

"PolicyRule is treated as valid for all twelve months, and "

"only restricted by its TimePeriod property value and the "

"other Mask properties."),

ModelCorrespondence {

"CIM_PolicyTimePeriodCondition.TimePeriod",

"CIM_PolicyTimePeriodCondition.LocalOrUtcTime"}

]

uint8 MonthOfYearMask[];

[Octetstring, Description (

" The purpose of this property is to refine the valid time "

"period that is defined by the TimePeriod property, by "

"explicitly specifying in which days of the month the Policy"

"Rule is valid. These properties work together, "

"with the TimePeriod used to specify the overall time period "

"in which the PolicyRule is valid, and the DayOfMonthMask used "

"to pick out the days of the month during which the Rule "

"is valid.\n\n "

" "

"This property is formatted as an octet string, structured "

"as follows:\n"

" o a 4-octet length field, indicating the length of the "

" entire octet string; this field is always set to "

" 0x0000000C for this property; \n"

" o an 8-octet field consisting of 31 bits identifying "

" the days of the month counting from the beginning, "

" followed by 31 more bits identifying the days of the "

" month counting from the end, followed by 2 bits that "

" are always set to '0'. For each day, the value '1' "

" indicates that the policy is valid for that day, and "

" the value '0' indicates that it is not valid. \n\n"

" "

"The value 0x0000000C8000000100000000, for example, "

"indicates that a PolicyRule is valid on the first and "

"last days of the month.\n\n "

" "

"For months with fewer than 31 days, the digits corresponding "

"to days that the months do not have (counting in both "

"directions) are ignored.\n\n"

" "

"If a value for this property is not provided, then the "

"PolicyRule is treated as valid for all days of the month, and "

"only restricted by its TimePeriod property value and the "

"other Mask properties."),

ModelCorrespondence {

"CIM_PolicyTimePeriodCondition.TimePeriod",

"CIM_PolicyTimePeriodCondition.LocalOrUtcTime"}

]

uint8 DayOfMonthMask[];

[Octetstring, Description (

" The purpose of this property is to refine the valid time "

"period that is defined by the TimePeriod property, by "

"explicitly specifying in which days of the month the Policy"

"Rule is valid. These properties work together, "

"with the TimePeriod used to specify the overall time period "

"in which the PolicyRule is valid, and the DayOfWeekMask used "

"to pick out the days of the week during which the Rule "

"is valid.\n\n "

" "

"This property is formatted as an octet string, structured "

"as follows:\n "

" o a 4-octet length field, indicating the length of the "

" entire octet string; this field is always set to "

" 0x00000005 for this property;\n"

" o a 1-octet field consisting of 7 bits identifying the 7 "

" days of the week, beginning with Sunday and ending with "

" Saturday, followed by 1 bit that is always set to '0'. "

" For each day of the week, the value '1' indicates that "

" the policy is valid for that day, and the value '0' "

" indicates that it is not valid. \n\n"

" "

"The value 0x000000057C, for example, indicates that a "

"PolicyRule is valid Monday through Friday.\n\n"

" "

"If a value for this property is not provided, then the "

"PolicyRule is treated as valid for all days of the week, "

"and only restricted by its TimePeriod property value and "

"the other Mask properties."),

ModelCorrespondence {

"CIM_PolicyTimePeriodCondition.TimePeriod",

"CIM_PolicyTimePeriodCondition.LocalOrUtcTime"}

]

uint8 DayOfWeekMask[];

[Description (

" The purpose of this property is to refine the valid time "

"period that is defined by the TimePeriod property, by "

"explicitly specifying a range of times in a day during which "

"the PolicyRule is valid. These properties work "

"together, with the TimePeriod used to specify the overall "

"time period in which the PolicyRule is valid, and the "

"TimeOfDayMask used to pick out the range of time periods "

"in a given day of during which the Rule is valid. \n\n"

" "

"This property is formatted in the style of RFC2445: a "

"time string beginning with the character 'T', followed by "

"the solidus character '/', followed by a second time string. "

"The first time indicates the beginning of the range, while "

"the second time indicates the end. Times are expressed as "

"substrings of the form 'Thhmmss'. \n\n"

" "

"The second substring always identifies a later time than "

"the first substring. To allow for ranges that span "

"midnight, however, the value of the second string may be "

"smaller than the value of the first substring. Thus, "

"'T080000/T210000' identifies the range from 0800 until 2100, "

"while 'T210000/T080000' identifies the range from 2100 until "

"0800 of the following day. \n\n"

" "

"When a range spans midnight, it by definition includes "

"parts of two successive days. When one of these days is "

"also selected by either the MonthOfYearMask, "

"DayOfMonthMask, and/or DayOfWeekMask, but the other day is "

"not, then the policy is active only during the portion of "

"the range that falls on the selected day. For example, if "

"the range extends from 2100 until 0800, and the day of "

"week mask selects Monday and Tuesday, then the policy is "

"active during the following three intervals:\n"

" From midnight Sunday until 0800 Monday; \n"

" From 2100 Monday until 0800 Tuesday; \n"

" From 2100 Tuesday until 23:59:59 Tuesday. \n\n"

" "

"If a value for this property is not provided, then the "

"PolicyRule is treated as valid for all hours of the day, "

"and only restricted by its TimePeriod property value and "

"the other Mask properties."),

ModelCorrespondence {

"CIM_PolicyTimePeriodCondition.TimePeriod",

"CIM_PolicyTimePeriodCondition.LocalOrUtcTime"}

]

string TimeOfDayMask;

[Description (

" This property indicates whether the times represented "

"in the TimePeriod property and in the various Mask "

"properties represent local times or UTC times. There is "

"no provision for mixing of local times and UTC times: the "

"value of this property applies to all of the other "

"time-related properties."),

ValueMap { "1", "2" },

Values { "localTime", "utcTime" },

ModelCorrespondence {

"CIM_PolicyTimePeriodCondition.TimePeriod",

"CIM_PolicyTimePeriodCondition.MonthOfYearMask",

"CIM_PolicyTimePeriodCondition.DayOfMonthMask",

"CIM_PolicyTimePeriodCondition.DayOfWeekMask",

"CIM_PolicyTimePeriodCondition.TimeOfDayMask"}

]

uint16 LocalOrUtcTime;

};

// ==================================================================

// PolicyRuleValidityPeriod

// ==================================================================

[Association, Aggregation, Description (

"The PolicyRuleValidityPeriod aggregation represents "

"scheduled activation and deactivation of a PolicyRule. "

"If a PolicyRule is associated with multiple policy time "

"periods via this association, then the Rule is active if "

"at least one of the time periods indicates that it is "

"active. (In other words, the PolicyTimePeriodConditions "

"are ORed to determine whether the Rule is active.) A Time"

"Period may be aggregated by multiple PolicyRules. A Rule "

"that does not point to a PolicyTimePeriodCondition via this "

"association is, from the point of view of scheduling, "

"always active. It may, however, be inactive for other "

"reasons. For example, the Rule's Enabled property may "

"be set to \"disabled\" (value=2).")

]

class CIM_PolicyRuleValidityPeriod : CIM_PolicyComponent

{

[Override ("GroupComponent"), Aggregate, Description (

"This property contains the name of a PolicyRule that "

"contains one or more PolicyTimePeriodConditions.")

]

CIM_PolicyRule REF GroupComponent;

[Override ("PartComponent"), Description (

"This property contains the name of a "

"PolicyTimePeriodCondition defining the valid time periods "

"for one or more PolicyRules.")

]

CIM_PolicyTimePeriodCondition REF PartComponent;

};

// ==================================================================

// VendorPolicyCondition

// ==================================================================

[Description (

" A class that provides a general extension mechanism for "

"representing PolicyConditions that have not been modeled "

"with specific properties. Instead, the two properties "

"Constraint and ConstraintEncoding are used to define the "

"content and format of the Condition, as explained below.\n\n"

" "

"As its name suggests, VendorPolicyCondition is intended for "

"vendor-specific extensions to the Policy Core Information "

"Model. Standardized extensions are not expected to use "

"this class.")

]

class CIM_VendorPolicyCondition : CIM_PolicyCondition

{

[Octetstring, Description (

"This property provides a general extension mechanism for "

"representing PolicyConditions that have not been "

"modeled with specific properties. The format of the "

"octet strings in the array is left unspecified in "

"this definition. It is determined by the OID value "

"stored in the property ConstraintEncoding. Since "

"ConstraintEncoding is single-valued, all the values of "

"Constraint share the same format and semantics."),

ModelCorrespondence {

"CIM_VendorPolicyCondition.ConstraintEncoding"}

]

string Constraint [];

[Description (

"An OID encoded as a string, identifying the format "

"and semantics for this instance's Constraint property."),

ModelCorrespondence {

"CIM_VendorPolicyCondition.Constraint"}

]

string ConstraintEncoding;

};

// ==================================================================

// PolicyAction

// ==================================================================

[Abstract, Description (

"A class representing a rule-specific or reusable policy "

"action to be performed if the PolicyConditions for a Policy"

"Rule evaluate to TRUE. Since all operational details of a "

"PolicyAction are provided in subclasses of this object, "

"this class is abstract.")

]

class CIM_PolicyAction : CIM_Policy

{

[Key, MaxLen (256), Description (

" The name of the class or the subclass used in the "

"creation of the System object in whose scope this "

"PolicyAction is defined. \n\n"

" "

"This property helps to identify the System object in "

"whose scope this instance of PolicyAction exists. "

"For a rule-specific PolicyAction, this is the System "

"in whose context the PolicyRule is defined. For a "

"reusable PolicyAction, this is the instance of "

"PolicyRepository (which is a subclass of System) that "

"holds the Action. \n\n"

" "

"Note that this property, and the analogous property "

"SystemName, do not represent propagated keys from an "

"instance of the class System. Instead, they are "

"properties defined in the context of this class, which "

"repeat the values from the instance of System to which "

"this PolicyAction is related, either directly via the "

"PolicyActionInPolicyRepository aggregation or indirectly "

"via the PolicyActionInPolicyRule aggregation.")

]

string SystemCreationClassName;

[Key, MaxLen (256), Description (

" The name of the System object in whose scope this "

"PolicyAction is defined. \n\n"

" "

"This property completes the identification of the System "

"object in whose scope this instance of PolicyAction "

"exists. For a rule-specific PolicyAction, this is the "

"System in whose context the PolicyRule is defined. For "

"a reusable PolicyAction, this is the instance of "

"PolicyRepository (which is a subclass of System) that "

"holds the Action.")

]

string SystemName;

[Key, MaxLen (256), Description (

"For a rule-specific PolicyAction, the CreationClassName "

"of the PolicyRule object with which this Action is "

"associated. For a reusable PolicyAction, a "

"special value, 'NO RULE', should be used to "

"indicate that this Action is reusable and not "

"associated with a single PolicyRule.")

]

string PolicyRuleCreationClassName;

[Key, MaxLen (256), Description (

"For a rule-specific PolicyAction, the name of "

"the PolicyRule object with which this Action is "

"associated. For a reusable PolicyAction, a "

"special value, 'NO RULE', should be used to "

"indicate that this Action is reusable and not "

"associated with a single PolicyRule.")

]

string PolicyRuleName;

[Key, MaxLen (256), Description (

"CreationClassName indicates the name of the class or the "

"subclass used in the creation of an instance. When used "

"with the other key properties of this class, this property "

"allows all instances of this class and its subclasses to "

"be uniquely identified.") ]

string CreationClassName;

[Key, MaxLen (256), Description (

"A user-friendly name of this PolicyAction.")

]

string PolicyActionName;

};

// ==================================================================

// PolicyActionInPolicyRepository

// ==================================================================

[Association, Description (

" A class representing the hosting of reusable "

"PolicyActions by a PolicyRepository. A reusable Policy"

"Action is always related to a single PolicyRepository, "

"via this aggregation.\n\n"

" "

"Note, that an instance of PolicyAction can be either "

"reusable or rule-specific. When the Action is rule-"

"specific, it shall not be related to any "

"PolicyRepository via the PolicyActionInPolicyRepository "

"aggregation.")

]

class CIM_PolicyActionInPolicyRepository : CIM_PolicyInSystem

{

[Override ("Antecedent"), Max(1), Description (

"This property represents a PolicyRepository "

"hosting one or more PolicyActions. A reusable "

"PolicyAction is always related to exactly one "

"PolicyRepository via the PolicyActionInPolicyRepository "

"aggregation. The [0..1] cardinality for this property "

"covers the two types of PolicyActions: 0 for a "

"rule-specific PolicyAction, 1 for a reusable one.")

]

CIM_PolicyRepository REF Antecedent;

[Override ("Dependent"), Description (

"This property holds the name of a PolicyAction"

"hosted in the PolicyRepository. ")

]

CIM_PolicyAction REF Dependent;

};

// ==================================================================

// PolicyActionInPolicyRule

// ==================================================================

[Association, Aggregation, Description (

" A PolicyRule aggregates zero or more instances of the "

"PolicyAction class, via the PolicyActionInPolicyRule "

"association. A Rule that aggregates zero Actions is not "

"valid -- it may, however, be in the process of being entered "

"into a PolicyRepository or being defined for a System. "

"Alternately, the actions of the policy may be explicit in "

"the definition of the PolicyRule. Note that a PolicyRule "

"should have no effect until it is valid.\n\n"

" "

"The Actions associated with a PolicyRule may be given a "

"required order, a recommended order, or no order at all. For "

"Actions represented as separate objects, the PolicyActionIn"

"PolicyRule aggregation can be used to express an order. \n\n"

" "

"This aggregation does not indicate whether a specified "

"action order is required, recommended, or of no significance; "

"the property SequencedActions in the aggregating instance of "

"PolicyRule provides this indication.")

]

class CIM_PolicyActionInPolicyRule : CIM_PolicyComponent

{

[Override ("GroupComponent"), Aggregate, Description (

"This property represents the PolicyRule that "

"contains one or more PolicyActions.")

]

CIM_PolicyRule REF GroupComponent;

[Override ("PartComponent"), Description (

"This property holds the name of a PolicyAction "

"contained by one or more PolicyRules.")

]

CIM_PolicyAction REF PartComponent;

[Description (

" This property provides an unsigned integer 'n' that"

"indicates the relative position of a PolicyAction in the "

"sequence of actions associated with a PolicyRule. "

"When 'n' is a positive integer, it indicates a place "

"in the sequence of actions to be performed, with "

"smaller integers indicating earlier positions in the "

"sequence. The special value '0' indicates 'don't care'. "

"If two or more PolicyActions have the same non-zero "

"sequence number, they may be performed in any order, but "

"they must all be performed at the appropriate place in the "

"overall action sequence. \n\n"

" "

"A series of examples will make ordering of PolicyActions "

"clearer: \n"

" o If all actions have the same sequence number, "

" regardless of whether it is '0' or non-zero, any "

" order is acceptable.\n "

" o The values: \n"

" 1:ACTION A \n"

" 2:ACTION B \n"

" 1:ACTION C \n"

" 3:ACTION D \n"

" indicate two acceptable orders: A,C,B,D or C,A,B,D, "

" since A and C can be performed in either order, but "

" only at the '1' position. \n"

" o The values: \n"

" 0:ACTION A \n"

" 2:ACTION B \n"

" 3:ACTION C \n"

" 3:ACTION D \n"

" require that B,C, and D occur either as B,C,D or as "

" B,D,C. Action A may appear at any point relative to "

" B, C, and D. Thus the complete set of acceptable "

" orders is: A,B,C,D; B,A,C,D; B,C,A,D; B,C,D,A; "

" A,B,D,C; B,A,D,C; B,D,A,C; B,D,C,A. \n\n"

" "

"Note that the non-zero sequence numbers need not start "

"with '1', and they need not be consecutive. All that "

"matters is their relative magnitude.")

]

uint16 ActionOrder;

};

// ==================================================================

// VendorPolicyAction

// ==================================================================

[Description (

" A class that provides a general extension mechanism for "

"representing PolicyActions that have not been modeled "

"with specific properties. Instead, the two properties "

"ActionData and ActionEncoding are used to define the "

"content and format of the Action, as explained below.\n\n"

" "

"As its name suggests, VendorPolicyAction is intended for "

"vendor-specific extensions to the Policy Core Information "

"Model. Standardized extensions are not expected to use "

"this class.") ]

class CIM_VendorPolicyAction : CIM_PolicyAction

{

[Octetstring, Description (

"This property provides a general extension mechanism for "

"representing PolicyActions that have not been "

"modeled with specific properties. The format of the "

"octet strings in the array is left unspecified in "

"this definition. It is determined by the OID value "

"stored in the property ActionEncoding. Since "

"ActionEncoding is single-valued, all the values of "

"ActionData share the same format and semantics."),

ModelCorrespondence {

"CIM_VendorPolicyAction.ActionEncoding"}

]

string ActionData [];

[Description (

"An OID encoded as a string, identifying the format "

"and semantics for this instance's ActionData property."),

ModelCorrespondence {

"CIM_VendorPolicyAction.ActionData"}

]

string ActionEncoding;

};

// ===================================================================

// end of file

// ===================================================================

15. Full Copyright Statement

Copyright (C) The Internet Society (2001). All Rights Reserved.

This document and translations of it may be copied and furnished to

others, and derivative works that comment on or otherwise explain it

or assist in its implementation may be prepared, copied, published

and distributed, in whole or in part, without restriction of any

kind, provided that the above copyright notice and this paragraph are

included on all such copies and derivative works. However, this

document itself may not be modified in any way, such as by removing

the copyright notice or references to the Internet Society or other

Internet organizations, except as needed for the purpose of

developing Internet standards in which case the procedures for

copyrights defined in the Internet Standards process must be

followed, or as required to translate it into languages other than

English.

The limited permissions granted above are perpetual and will not be

revoked by the Internet Society or its successors or assigns.

This document and the information contained herein is provided on an

"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING

TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING

BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION

HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF

MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

Funding for the RFCEditor function is currently provided by the

Internet Society.

 
 
 
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