RFC2731 - Encoding Dublin Core Metadata in HTML

Network Working Group J. Kunze

Request for Comments: 2731 Dublin Core

Category: Informational Metadata Initiative

December 1999

Encoding Dublin Core Metadata in Html

Status of this Memo

This memo provides information for the Internet community. It does

not specify an Internet standard of any kind. Distribution of this

memo is unlimited.

1. Abstract

The Dublin Core [DC1] is a small set of metadata elements for

describing information resources. This document eXPlains how these

elements are expressed using the META and LINK tags of HTML

[HTML4.0]. A sequence of metadata elements embedded in an HTML file

is taken to be a description of that file. Examples illustrate

conventions allowing interoperation with current software that

indexes, displays, and manipulates metadata, sUCh as [SWISH-E],

[freeWAIS-sf2.0], [GLIMPSE], [HARVEST], [ISEARCH], etc., and the Perl

[PERL] scripts in the appendix.

2. HTML, Dublin Core, and Non-Dublin Core Metadata

The Dublin Core (DC) metadata initiative [DCHOME] has produced a

small set of resource description categories [DC1], or elements of

metadata (literally, data about data). Metadata elements are

typically small relative to the resource they describe and may, if

the resource format permits, be embedded in it. Two such formats are

the Hypertext Markup Language (HTML) and the Extensible Markup

Language (XML); HTML is currently in wide use, but once standardized,

XML [XML] in conjunction with the Resource Description Framework

[RDF] promise a significantly more expressive means of encoding

metadata. The [RDF] specification actually describes a way to use

RDF within an HTML document by adhering to an abbreviated syntax.

This document explains how to encode metadata using HTML 4.0

[HTML4.0]. It is not concerned with element semantics, which are

defined elsewhere. For illustrative purposes, some element semantics

are alluded to, but in no way should semantics appearing here be

considered definitive.

The HTML encoding allows elements of DC metadata to be interspersed

with non-DC elements (provided such mixing is consistent with rules

governing use of those non-DC elements). A DC element is indicated

by the prefix "DC", and a non-DC element by another prefix; for

example, the prefix "AC" is used with elements from the A-Core [AC].

3. The META Tag

The META tag of HTML is designed to encode a named metadata element.

Each element describes a given ASPect of a document or other

information resource. For example, this tagged metadata element,

content = "Simpson, Homer">

says that Homer Simpson is the Creator, where the element named

Creator is defined in the DC element set. In the more general form,

content = "ELEMENT_VALUE">

the capitalized Words are meant to be replaced in actual

descriptions; thus in the example,

ELEMENT_NAME was: Creator

ELEMENT_VALUE was: Simpson, Homer

and PREFIX was: DC

Within a META tag the first letter of a Dublin Core element name is

capitalized. DC places no restriction on alphabetic case in an

element value and any number of META tagged elements may appear

together, in any order. More than one DC element with the same name

may appear, and each DC element is optional. The next example is a

book description with two authors, two titles, and no other metadata.

content = "The Communist Manifesto">

content = "Marx, K.">

content = "Engels, F.">

content = "Capital">

The prefix "DC" precedes each Dublin Core element encoded with META,

and it is separated by a period (.) from the element name following

it. Each non-DC element should be encoded with a prefix that can be

used to trace its origin and definition; the linkage between prefix

and element definition is made with the LINK tag, as explained in the

next section. Non-DC elements, such as Email from the A-Core [AC],

may appear together with DC elements, as in

content = "Da Costa, José">

content = "dacostaj@peoplesmail.org">

content = "Jesse "The Body" Ventura--A Biography">

This example also shows how some special characters may be encoded.

The author name in the first element contains a diacritic encoded as

an HTML character entity reference -- in this case an accented letter

E. Similarly, the last line contains two double-quote characters

encoded so as to avoid being interpreted as element content

delimiters.

4. The LINK Tag

The LINK tag of HTML may be used to associate an element name prefix

with the reference definition of the element set that it identifies.

A sequence of META tags describing a resource is incomplete without

one such LINK tag for each different prefix appearing in the

sequence. The previous example could be considered complete with the

addition of these two LINK tags:

href = "http://purl.org/DC/elements/1.0/">

href = "http://metadata.net/ac/2.0/">

In general, the association takes the form

href = "LOCATION_OF_DEFINITION">

where, in actual descriptions, PREFIX is to be replaced by the prefix

and LOCATION_OF_DEFINITION by the URL or URN of the defining

document. When embedded in the HEAD part of an HTML file, a sequence

of LINK and META tags describes the information in the surrounding

HTML file itself. Here is a complete HTML file with its own embedded

description.

<html>

<head>

<title> A Dirge </title>

href = "http://purl.org/DC/elements/1.0/">

content = "A Dirge">

content = "Shelley, Percy Bysshe">

content = "poem">

content = "1820">

content = "text/html">

content = "en">

</head>

Rough wind, that moanest loud

Grief too sad for song;

Wild wind, when sullen cloud

Knells all the night long;

Sad storm, whose tears are vain,

Bare woods, whose branches strain,

Deep caves and dreary main, -

Wail, for the world's wrong!

</pre></body>

</html>

5. Encoding Recommendations

HTML allows more flexibility in principle and in practice than is

recommended here for encoding metadata. Limited flexibility

encourages easy development of software for extracting and processing

metadata. At this early evolutionary stage of internet metadata,

easy prototyping and experimentation hastens the development of

useful standards.

Adherence is therefore recommended to the tagging style exemplified

in this document as regards prefix and element name capitalization,

double-quoting (") of attribute values, and not starting more than

one META tag on a line. There is much room for flexibility, but

choosing a style and sticking with it will likely make metadata

manipulation and editing easier. The following META tags adhere to

the recommendations and carry identical metadata in three different

styles:

<META NAME="DC.Format"

CONTENT="text/html; 12 Kbytes">

<meta

Content = "text/html; 12 Kbytes"

Name = "DC.Format"

Use of these recommendations is known to result in metadata that may

be harvested, indexed, and manipulated by popular, freely available

software packages such as [SWISH-E], [freeWAIS-sf2.0], [GLIMPSE],

[HARVEST], and [ISEARCH], among others. These conventions also work

with the metadata processing scripts appearing in the appendix, as

well as with most of the [DCPROJECTS] applications referenced from

the [DCHOME] site. Software support for the LINK tag and qualifier

conventions (see the next section) is not currently widespread.

Ordering of metadata elements is not preserved in general. Writers

of software for metadata indexing and display should try to preserve

relative ordering among META tagged elements having the same name

(e.g., among multiple authors), however, metadata providers and

searchers have no guarantee that ordering will be preserved in

metadata that passes through unknown systems.

6. Dublin Core in Real Descriptions

In actual resource description it is often necessary to qualify

Dublin Core elements to add nuances of meaning. While neither the

general principles nor the specific semantics of DC qualifiers are

within scope of this document, everyday uses of the qualifier syntax

are illustrated to lend realism to later examples. Without further

explanation, the three ways in which the optional qualifier syntax is

currently (subject to change) used to supplement the META tag may be

summarized as follows:

Accordingly, a posthumous work in Spanish might be described with

scheme = "rfc1766"

content = "es">

lang = "es"

content = "La Mesa Verde y la Silla Roja">

lang = "en"

content = "The Green Table and the Red Chair">

content = "1935">

content = "1939">

Note that the qualifier syntax and label suffixes (which follow an

element name and a period) used in examples in this document merely

reflect current trends in the HTML encoding of qualifiers. Use of

this syntax and these suffixes is neither a standard nor a

recommendation.

7. Encoding Dublin Core Elements

This section consists of very simple Dublin Core encoding examples,

arranged by element.

Title (name given to the resource)

-----

content = "Polycyclic aromatic hydrocarbon contamination">

content = "Crime and Punishment">

content = "Methods of Information in Medicine, Vol 32, No 4">

content = "Still life #4 with flowers">

lang = "de"

content = "Das Wohltemperierte Klavier, Teil I">

Creator (entity that created the content)

-------

content = "Gogh, Vincent van">

content = "van Gogh, Vincent">

content = "Mao Tse Tung">

content = "Mao, Tse Tung">

content = "Plato">

lang = "fr"

content = "Platon">

content = "Sturges, Preston">

content = "Hecht, Ben">

content = "Chaplin, Charles">

Subject (topic or keyword)

-------

content = "heart attack">

scheme = "MESH"

content = "Myocardial Infarction; Pericardial Effusion">

content = "vietnam war">

scheme = "LCSH"

content = "Vietnamese Conflict, 1961-1975">

content = "Friendship">

scheme = "ddc"

content = "158.25">

Description (account, summary, or abstract of the content)

-----------

lang = "en"

content = "The Author gives some Account of Himself and Family

-- His First Inducements to Travel -- He is

Shipwrecked, and Swims for his Life -- Gets safe on

Shore in the Country of Lilliput -- Is made a

Prisoner, and carried up the Country">

content = "A tutorial and reference manual for Java.">

content = "Seated family of five, coconut trees to the left,

sailboats moored off sandy beach to the right,

with volcano in the background.">

Publisher (entity that made the resource available)

---------

content = "O'Reilly">

content = "Digital Equipment Corporation">

content = "University of California Press">

content = "State of Florida (USA)">

Contributor (other entity that made a contribution)

-----------

content = "Curie, Marie">

content = "Adams, Ansel">

content = "Sendak, Maurice">

content = "Starr, Kenneth">

Date (of an event in the life of the resource; [WTN8601] recommended)

----

content = "1972">

content = "1998-05-14">

scheme = "WTN8601"

content = "1998-05-14">

content = "1998-05-14">

content = "1998-05-21">

content = "1998-05-28">

content = "triassic">

content = "1957">

scheme = "WTN8601"

content = "1998-12-02T16:59">

scheme = "ISO8601"

content = "98-W49-3T1659">

scheme = "ANSI.X3.X30-1985"

content = "19980514">

Type (nature, genre, or category; [DCT1] recommended)

----

content = "poem">

scheme = "DCT1"

content = "software">

content = "software program source code">

content = "interactive video game">

scheme = "DCT1"

content = "dataset">

content = "web home page">

content = "web bibliography">

content = "painting">

content = "image; woodblock">

scheme = "AAT"

content = "clipeus (portrait)">

lang = "en-US"

content = "image; advertizement">

scheme = "DCT1"

content = "event">

content = "event; periodic">

Format (physical or digital data format, plus optional dimensions)

------

content = "text/xml">

scheme = "IMT"

content = "text/xml">

scheme = "IMT"

content = "image/jpeg">

content = "A text file with mono-spaced tables and diagrams.">

content = "video/mpeg; 14 minutes">

content = "unix tar archive, gzip compressed; 1.5 Mbytes">

content = "watercolor; 23 cm x 31 cm">

Identifier (of the resource)

----------

content = "http://foo.bar.org/zaf/">

content = "urn:ietf:rfc:1766">

scheme = "ISBN"

content = "1-56592-149-6">

scheme = "LCCN"

content = "67-26020">

scheme = "DOI"

content = "10.12345/33-824688ab">

Source (reference to the resource's origin)

------

content = "Shakespeare's Romeo and Juliet">

content = "http://a.b.org/manon/">

Language (of the content of the resource; [RFC1766] recommended)

--------

content = "en">

scheme = "rfc1766"

content = "en">

scheme = "ISO639-2"

content = "eng">

scheme = "rfc1766"

content = "en-US">

content = "zh">

content = "ja">

content = "es">

content = "de">

content = "german">

lang = "fr"

content = "allemand">

Relation (reference to a related resource)

--------

content = "http://foo.bar.org/abc/proceedings/1998/">

content = "http://foo.bar.org/cd145.sgml">

content = "http://foo.bar.org/draft9.4.4.2">

content = "urn:isbn:1-56592-149-6">

content = "Shakespeare's Romeo and Juliet">

content = "LWP::UserAgent; HTML::Parse; URI::URL;

Net::DNS; Tk::Pixmap; Tk::Bitmap; Tk::Photo">

Coverage (extent or scope of the content)

--------

content = "US civil war era; 1861-1865">

content = "Columbus, Ohio, USA; Lat: 39 57 N Long: 082 59 W">

scheme = "TGN"

content = "Columbus (C,V)">

content = "Commonwealth of Australia">

Rights (text or identifier of a rights management statement)

------

lang = "en"

content = "http://foo.bar.org/cgi-bin/terms">

8. Security Considerations

The syntax rules for encoding Dublin Core metadata in HTML that are

documented here pose no direct risk to computers and networks.

People can use these rules to encode metadata that is inaccurate or

even deliberately misleading (creating mischief in the form of "index

spam"), however, this reflects a general pattern of HTML META tag

abuse that is not limited to the encoding of metadata from the Dublin

Core set. Even traditional metadata encoding schemes (e.g., [MARC])

are not immune to inaccuracy, although they are generally followed in

environments where production quality greatly exceeds that of the

average Web site.

Systems that process metadata encoded with META tags need to consider

issues related to its accuracy and validity as part of their design

and implementation, and users of such systems need to consider the

design and implementation assumptions. Various approaches may be

relevant for certain applications, such as adding statements of

metadata provenance, signing of metadata with digital signatures, and

automating certain aspects of metadata creation; but these are far

outside the scope of this document and the underlying META tag syntax

that it describes.

9. Appendix -- Perl Scripts that Manipulate HTML Encoded Metadata

This section contains two simple programs that work with versions 4

and 5 of the Perl [PERL] scripting language interpreter. They may be

taken and freely adapted for local organizational needs, research

proposals, venture capital bids, etc. A variety of applications are

within easy reach of implementors that choose to build on these

scripts.

Script 1: Metadata Format Conversion

-------------------------------------

Here is a simple Perl script that correctly recognizes every example

of metadata encoding in this document. It shows how a modest

scripting effort can produce a utility that converts metadata from

one format to another. Minor changes are sufficient to support a

number of output formats.

#!/depot/bin/perl

# This simple perl script extracts metadata embedded in an HTML file

# and outputs it in an alternate format. Issues warning about missing

# element name or value.

# Handles mixed case tags and attribute values, one per line or spanning

# several lines. Also handles a quoted string spanning multiple lines.

# No error checking. Does not tolerate more than one "<meta" per line.

print "@(urc;\n";

while (<>) {

next if (! /<meta/i);

($meta) = /(<meta.*$)/i;

if (! /<meta.*>/i) {

while (<>) {

$meta .= $_;

last if (/>/);

}

$name = $meta =~ /name\s*=\s*"([^"]*)"/i

? $1 : "MISSING ELEMENT NAME";

$content = $meta =~ /content\s*=\s*"([^"]*)"/i

? $1 : "MISSING ELEMENT VALUE";

($scheme) = $meta =~ /scheme\s*=\s*"([^"]*)"/i;

($lang) = $meta =~ /lang\s*=\s*"([^"]*)"/i;

if ($lang $scheme) {

$mod = " ($lang";

if (! $scheme)

{ $mod .= ")"; }

elsif (! $lang)

{ $mod .= "$scheme)" }

else

{ $mod .= ", $scheme)"; }

}

else

{ $mod = ""; }

print " @$name$mod; $content\n";

}

print "@)urc;\n";

# ---- end of Perl script ----

When the conversion script is run on the metadata file example from

the LINK tag section (section 4), it produces the following output.

@(urc;

@DC.Title; A Dirge

@DC.Creator; Shelley, Percy Bysshe

@DC.Type; poem

@DC.Date; 1820

@DC.Format; text/html

@DC.Language; en

@)urc;

Script 2: Automated Metadata Creation

--------------------------------------

The creation and maintenance of high-quality metadata can be

extremely expensive without automation to assist in processes such as

supplying pre-set or computed defaults, validating syntax, verifying

value ranges, spell checking, etc. Considerable relief could be had

from a script that reduced an individual provider's metadata burden

to just the title of each document. Below is such a script. It lets

the provider of an HTML document abbreviate an entire embedded

resource description using a single HTML comment statement that looks

Our script processes this statement specially as a kind of "metadata

block" declaration with attached title. The general form is

This statement works much like a "Web server-side include" in that

the script replaces it with a fully-specified block of metadata and

triggers other replacements. Once installed, the script can output

HTML files suitable for integration into one's production Web server

procedures.

The individual provider keeps a separate "template" file of

infrequently changing pre-set values for metadata elements. If the

provider's needs are simple enough, the only element values besides

the title that differ from one document to the next may be generated

automatically. Using the script, values may be referenced as

variables from within the template or within the document. Our

variable references have the form "(--mbVARNAME)", and here is what

they look like inside a template:

<title> (--mBTitle) </title>

content = "Simpson, Homer">

content = "(--mbtitle)">

content = "(--mbfilemodtime)">

content = "(--mbbaseURL)/(--mbfilename)">

content = "text/html; (--mbfilesize)">

content = "(--mblanguage)-BUREAUCRATESE">

content = "Springfield Nuclear">

href = "http://purl.org/DC/elements/1.0/">

href = "http://nukes.org/ReactorCore/rc">

The above template represents the metadata block that will describe

the document once the variable references are replaced with real

values. By the conventions of our script, the following variables

will be replaced in both the template and in the document:

(--mbfilesize) size of the final output file

(--mbtitle) title of the document

(--mblanguage) language of the document

(--mbbaseURL) beginning part of document identifier

(--mbfilename) last part (minus .html) of identifier

(--mbfilemodtime) last modification date of the document

Here's an example HTML file to run the script on.

<html>

<head>

content = "Memorandum">

</head>

<body>

<p>

From: Acting Shift Supervisor

To: Plant Control Personnel

RE: (--mbtitle)

Date: (--mbfilemodtime)

<p>

Pursuant to directive DOH:10.2001/405aec of article B-2022,

subsection 48.2.4.4.1c regarding staff morale and employee

productivity standards, the current allocation of doughnut

acquisition funds shall be increased effective immediately.

</body>

</html>

Note that because replacement occurs throughout the document, the

provider need only enter the title once instead of twice (normally

the title must be entered once in the HTML head and again in the HTML

body). After running the script, the above file is transformed into

this:

<html>

<head>

<title> Nutritional Allocation Increase </title>

content = "Simpson, Homer">

content = "Nutritional Allocation Increase">

content = "1999-03-08">

content = "http://moes.bar.com/doh/homer.html">

content = "text/html; 1320 bytes">

content = "en-BUREAUCRATESE">

content = "Springfield Nuclear">

href = "http://purl.org/DC/elements/1.0/">

href = "http://nukes.org/ReactorCore/rc">

content = "Memorandum">

</head>

<body>

<p>

From: Acting Shift Supervisor

To: Plant Control Personnel

RE: Nutritional Allocation Increase

Date: 1999-03-08

<p>

Pursuant to directive DOH:10.2001/405aec of article B-2022,

subsection 48.2.4.4.1c regarding staff morale and employee

productivity standards, the current allocation of doughnut

acquisition funds shall be increased effective immediately.

</body>

</html>

Here is the script that accomplishes this transformation.

#!/depot/bin/perl

# This Perl script processes metadata block declarations of the form

#  and variable references of the

# form (--mbVARNAME), replacing them with full metadata blocks and

# variable values, respectively. Requires a "template" file.

# Outputs an HTML file.

# Invoke this script with a single filename argument, "foo". It creates

# an output file "foo.html" using a temporary working file "foo.work".

# The size of foo.work is measured after variable replacement, and is

# later inserted into the file in such a way that the file's size does

# not change in the process. Has little or no error checking.

$infile = shift;

open(IN, "< $infile")

or die("Could not open input file \"$infile\"");

$workfile = "$infile.work";

unlink($workfile);

open(WORK, "+> $workfile")

or die("Could not open work file \"$workfile\"");

@offsets = (); # records locations for late size replacement

$title = ""; # gets the title during metablock processing

$language = "en"; # pre-set language here (not in the template)

$baseURL = "http://moes.bar.com/doh"; # pre-set base URL here also

$filename = "$infile.html"; # final output filename

$filesize = "(--mbfilesize)"; # replaced late (separate pass)

($year, $month, $day) = (localtime( (stat IN) [9] ))[5, 4, 3];

$filemodtime = sprintf "%s-%02s-%02s", 1900 + $year, 1 + $month, $day;

sub putout { # outputs current line with variable replacement

if (! /\(--mb/) {

print WORK;

return;

}

if (/$--mbfilesize$/) # remember where it was

{ push @offsets, tell WORK; } # but don't replace yet

s/$--mbtitle$/$title/g;

s/$--mblanguage$/$language/g;

s/$--mbbaseURL$/$baseURL/g;

s/$--mbfilename$/$filename/g;

s/$--mbfilemodtime$/$filemodtime/g;

print WORK;

}

while (<IN>) { # main loop for input file

if (! /(.*)<!--metablock\s*(.*)/) {

&putout;

next;

}

$title = $2;

$_ = $1;

&putout;

if ($title =~ s/\s*-->(.*)//) {

$remainder = $1;

}

else {

while (<IN>) {

$title .= $_;

last if (/(.*)\s*-->(.*)/);

}

$title .= $1;

$remainder = $2;

}

open(TPLATE, "< template")

or die("Could not open template file");

while (<TPLATE>) # subloop for template file

{ &putout; }

close(TPLATE);

$_ = $remainder;

&putout;

}

close(IN);

# Now replace filesize variables without altering total byte count.

select( (select(WORK), $ = 1) [0] ); # first flush output so we

if (($size = -s WORK) < 100000) # can get final file size

{ $scale = 0; } # and set scale factor or

else { # compute it, keeping width of size field low

for ($scale = 0; $size >= 1000; $scale++)

{ $size /= 1024; }

}

$filesize = sprintf "%7.7s %sbytes",

$size, (" ", "K", "M", "G", "T", "P") [$scale];

foreach $pos (@offsets) { # loop through saved size locations

seek WORK, $pos, 0; # read the line found there

$_ = <WORK>;

# $filesize must be exactly as wide as "(--mbfilesize)"

s/$--mbfilesize$/$filesize/g;

seek WORK, $pos, 0; # rewrite it with replacement

print WORK;

}

close(WORK);

rename($workfile, "$filename")

or die("Could not rename \"$workfile\" to \"$filename\"");

# ---- end of Perl script ----

10. Author's Address

John A. Kunze

Center for Knowledge Management

University of California, San Francisco

530 Parnassus Ave, Box 0840

San Francisco, CA 94143-0840, USA

Fax: +1 415-476-4653

EMail: jak@ckm.ucsf.edu

11. References

[AAT] Art and Architecture Thesaurus, Getty Information

Institute.

http://shiva.pub.getty.edu/aat_browser/

[AC] The A-Core: Metadata about Content Metadata, (in

progress)

http://metadata.net/ac/draft-iannella-admin-01.txt

[DC1] Weibel, S., Kunze, J., Lagoze, C. and M. Wolf,

"Dublin Core Metadata for Resource Discovery", RFC

2413, September 1998.

FTP://ftp.isi.edu/in-notes/rfc2413.txt

[DCHOME] Dublin Core Initiative Home Page.

http://purl.org/DC/

[DCPROJECTS] Projects Using Dublin Core Metadata.

http://purl.org/DC/projects/index.htm

[DCT1] Dublin Core Type List 1, DC Type Working Group,

March 1999.

http://www.loc.gov/marc/typelist.html

[freeWAIS-sf2.0] The enhanced freeWAIS distribution, February 1999.

http://ls6-www.cs.uni-

dortmund.de/ir/projects/freeWAIS-sf/

[GLIMPSE] Glimpse Home Page.

http://glimpse.cs.arizona.edu/

[HARVEST] Harvest Web Indexing.

http://www.tardis.ed.ac.uk/harvest/

[HTML4.0] Hypertext Markup Language 4.0 Specification, April

1998.

http://www.w3.org/TR/REC-html40/

[ISEARCH] Isearch Resources Page.

http://www.etymon.com/Isearch/

[ISO639-2] Code for the representation of names of languages,

1996.

http://www.indigo.ie/egt/standards/iso639/iso639-2-

en.html

[ISO8601] ISO 8601:1988(E), Data elements and interchange

formats -- Information interchange -- Representation

of dates and times, International Organization for

Standardization, June 1988.

http://www.iso.ch/markete/8601.pdf

[MARC] USMARC Format for Bibliographic Data, US Library of

Congress.

http://lcweb.loc.gov/marc/marc.html

[PERL] L. Wall, T. Christiansen, R. Schwartz, Programming

Perl, Second Edition, O'Reilly, 1996.

[RDF] Resource Description Framework Model and Syntax

Specification, February 1999.

http://www.w3.org/TR/REC-rdf-syntax/

[RFC1766] Alvestrand, H., "Tags for the Identification of

Languages", RFC1766, March 1996.

ftp://ftp.isi.edu/in-notes/rfc1766.txt

[SWISH-E] Simple Web Indexing System for Humans - Enhanced.

http://sunsite.Berkeley.EDU/SWISH-E/

[TGN] Thesaurus of Geographic Names, Getty Information

Institute.

http://shiva.pub.getty.edu/tgn_browser/

[WTN8601] W3C Technical Note - Profile of ISO 8601 Date and

Time Formats.

http://www.w3.org/TR/NOTE-datetime

[XML] Extensible Markup Language (XML).

http://www.w3.org/TR/REC-xml

12. Full Copyright Statement

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

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