Network Working Group M. Nottingham
Internet-Draft April 9, 2003
Expires: October 8, 2003
RSS 2.0
draft-nottingham-rss2-00
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Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This specification documents version 2.0 of RSS, an XML-based format
for syndicating Web content and metadata.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Document terminology and conventions . . . . . . . . . . 3
2. Document Structure . . . . . . . . . . . . . . . . . . . 3
3. The rss Element . . . . . . . . . . . . . . . . . . . . 3
4. The channel Element . . . . . . . . . . . . . . . . . . 3
4.1 Required Children . . . . . . . . . . . . . . . . . . . 3
4.1.1 title Element . . . . . . . . . . . . . . . . . . . . . 4
4.1.2 link Element . . . . . . . . . . . . . . . . . . . . . . 4
4.1.3 description Element . . . . . . . . . . . . . . . . . . 4
4.2 Optional Children . . . . . . . . . . . . . . . . . . . 4
4.2.1 language Element . . . . . . . . . . . . . . . . . . . . 4
4.2.2 copyright Element . . . . . . . . . . . . . . . . . . . 4
4.2.3 managingEditor Element . . . . . . . . . . . . . . . . . 4
4.2.4 webMaster Element . . . . . . . . . . . . . . . . . . . 4
4.2.5 pubDate Element . . . . . . . . . . . . . . . . . . . . 4
4.2.6 lastBuildDate Element . . . . . . . . . . . . . . . . . 5
4.2.7 category Element . . . . . . . . . . . . . . . . . . . . 5
4.2.8 generator Element . . . . . . . . . . . . . . . . . . . 5
4.2.9 docs Element . . . . . . . . . . . . . . . . . . . . . . 5
4.2.10 cloud Element . . . . . . . . . . . . . . . . . . . . . 5
4.2.11 ttl Element . . . . . . . . . . . . . . . . . . . . . . 5
4.2.12 image Element . . . . . . . . . . . . . . . . . . . . . 5
4.2.13 rating Element . . . . . . . . . . . . . . . . . . . . . 6
4.2.14 textInput Element . . . . . . . . . . . . . . . . . . . 6
4.2.15 skipHours Element . . . . . . . . . . . . . . . . . . . 7
4.2.16 skipDays Element . . . . . . . . . . . . . . . . . . . . 7
4.3 The item Element . . . . . . . . . . . . . . . . . . . . 7
4.3.1 Optional Children . . . . . . . . . . . . . . . . . . . 7
4.3.1.1 title Element . . . . . . . . . . . . . . . . . . . . . 7
4.3.1.2 link Element . . . . . . . . . . . . . . . . . . . . . . 7
4.3.1.3 description Element . . . . . . . . . . . . . . . . . . 8
4.3.1.4 author Element . . . . . . . . . . . . . . . . . . . . . 8
4.3.1.5 category Element . . . . . . . . . . . . . . . . . . . . 8
4.3.1.6 comments Element . . . . . . . . . . . . . . . . . . . . 8
4.3.1.7 enclosure Element . . . . . . . . . . . . . . . . . . . 8
4.3.1.8 guid Element . . . . . . . . . . . . . . . . . . . . . . 8
4.3.1.9 pubDate Element . . . . . . . . . . . . . . . . . . . . 9
4.3.1.10 source Element . . . . . . . . . . . . . . . . . . . . . 9
5. Date Formatting . . . . . . . . . . . . . . . . . . . . 9
6. Extending RSS . . . . . . . . . . . . . . . . . . . . . 9
7. IANA Considerations . . . . . . . . . . . . . . . . . . 10
8. Security Considerations . . . . . . . . . . . . . . . . 10
References . . . . . . . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . 11
A. UserLand Copyright Statement . . . . . . . . . . . . . . 11
Intellectual Property and Copyright Statements . . . . . 13
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1. Introduction
This specification documents version 2.0 of RSS (Really Simple
Syndication), an XML-based format for syndicating Web content and
metadata.
This specification provides stable documentation for the RSS 2.0
format [9] as described by Dave Winer of UserLand Software, to assist
in implementation. As such, RSS documents conformant with this
specification should be conformant with that specification, and vice
versa.
[[[NOTE: This Internet-Draft is being made available ONLY to allow
the community to ascertain whether the specification described herein
is true to the original RSS 2.0 specification. Comments should be
directed to the RSS2 Support mailing list
(RSS2-Support@yahoogroups.com).]]]
1.1 Document terminology and conventions
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 RFC 2119 [5].
2. Document Structure
RSS documents MUST be conformant to the XML 1.0 specification [1].
There is explicitly no namespace URI [2] associated with the elements
described in this document.
3. The rss Element
The root (top-level) element of an RSS document MUST be the rss
element. It has one mandatory attribute, version, which indicates the
version of RSS which the document conforms to. Documents conformant
to this specification MUST have a version attribute of "2.0".
The rss element MUST contain a channel element.
4. The channel Element
The channel element contains metadata about the RSS channel, as well
as the items which comprise it.
4.1 Required Children
The following elements MUST be present as children of the channel
element;
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4.1.1 title Element
The title element MUST contain a string, to be used as a name for the
channel. Its content SHOULD be the same as that of the human-readable
Web page it refers to.
4.1.2 link Element
The link element MUST contain a URL [6] which indicates a
(human-readable) Web page associated with the channel.
4.1.3 description Element
The description element MUST contain a string describing the channel.
4.2 Optional Children
The following elements MAY be present as children of the channel
element;
4.2.1 language Element
The langauage element, if present, MUST contain a language tag, as
defined in RFC3066 [8].
4.2.2 copyright Element
The copyright element, if present, MUST contains a string, which
serves as copyright notice regarding the channel's content.
4.2.3 managingEditor Element
The managingEditor element, if present, MUST contain an e-mail
address, indicating the person or entity responsible for the content
(in an editorial sense).
4.2.4 webMaster Element
The webMaster element, if present, MUST contain an e-mail address,
indicating the person or entity responsible for the technical
administration of the channel.
4.2.5 pubDate Element
The pubDate element, if present, MUST contain an RFC822-formatted [4]
date (subject to the caveats below). It represents the publication
date for the channel.
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For example, the New York Times publishes on a daily basis, the
publication date flips once every 24 hours. That's when the pubDate
of the channel changes.
4.2.6 lastBuildDate Element
The lastBuildDate element, if present, MUST contain an
RFC822-formatted [4] date (subject to the caveats below). It
represents the moment when the content of the channel last changed.
4.2.7 category Element
The category element, when present, MUST contain a string that
identifies a categorization for the channel. It SHOULD use forward
slash delimitation to indicate hierarchy.
The category element MAY have a domain attribute, which MUST be a
string that identifies a categorization taxonomy.
The category element MAY be repeated to associate multiple
categorizations with a channel.
4.2.8 generator Element
The generator element, if present, MUST contain a string, indicating
the program used to generate the document.
4.2.9 docs Element
The docs element, if present, MUST contain a URL that resolves to
documentation for the format of the RSS file, for future reference.
4.2.10 cloud Element
The cloud element, if present, allows processes to register to be
notified of updates to the channel, by using a lightweight
publish-subscribe protocol.
For more information, see the rssCloud [10] interface.
4.2.11 ttl Element
The ttl element, when present, MUST contain an integer number of
minutes that indicates how long a channel's representation can be
cached.
4.2.12 image Element
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The image element, when present, allows an image such as an
illustration or photograph to be assocated with the channel. It MUST
have the following children: the url element, the title element, and
the link element.
The url element MUST contain a URL which can be used to locate the
image. It SHOULD be capable of returning an image with one of the
following media types; image/gif, image/jpeg, image/png.
The title element MUST be a string describing the image (this element
as the same semantic as the HTML alt attribute).
The link element MUST contain a URL which indicates the locatation of
the site associated with the image.
In practice, the title element and link element SHOULD be the same as
those associated with the channel itself.
Additionally, the image element MAY have the following children: the
width element and the height element.
Both the width element and the height element MUST contain integers
which indicate the width and height of the image in pixels,
respectively.
The value of the width element MUST NOT be greater than 144; if it is
not present, consumers MAY assume it to be 88.
The value of the height element MUST NOT be greater than 400; if it
is not present, consumers MAY assume it to be 31.
4.2.13 rating Element
The rating element, when present, MUST contain the PICS [3] rating
for the channel.
4.2.14 textInput Element
The textInput element describes a text input control that can be used
in conjunction with the channel. It MUST contain the following
children: the title element, the description element, the name
element and the link element. It is included in this specification
for backwards-compatibility.
The title element MUST contain a string that can be used as a label
for the text input submission widget.
The description element MUST contain a string that explains the text
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input area.
The name element MUST contain a string that associates a name with
the input text.
The link element MUST contain a URL to which the text can be
submitted.
4.2.15 skipHours Element
The skipHours element, if present, MUST contain one to 24 hour
elements.
The hour element MUST contain an integer between 0 and 23. Its value
indicates an hour in which consumers SHOULD NOT attempt to fetch
representations of the channel; a value of 0 indicates midnight GMT.
4.2.16 skipDays Element
The skipDays element, if present, MUST contain one to seven day
elements.
The day element MUST contain one of the following strings; "Monday",
"Tuesday", "Wednesday", "Thursday", "Friday", "Saturday" or "Sunday".
Its value indicates a day on which consumers SHOULD NOT attempt to
fetch representation of the channel.
4.3 The item Element
In addition to the required and optional children described above,
the channel element MAY have any number of item elements following
them.
item elements embody the payload of the RSS channel. Although all
item child elements described here are optional, each item MUST have
either a title element or description element as a child.
4.3.1 Optional Children
4.3.1.1 title Element
The title element, if present, MUST contain a string, to be used as a
name for the item.
4.3.1.2 link Element
The link element, if present, MUST contain a URL which indicates a
(human-readable) Web page associated with the item.
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4.3.1.3 description Element
The description element, if present, MUST contain a string describing
the item.
4.3.1.4 author Element
The author element, if present, MUST contain an e-mail addres,
indicating the author of the item.
For examples, publications syndicated via RSS might indicate the
person who wrote the article that the item describes. For
collaborative Weblogs, the author of the item might be different from
the managing editor or Webmaster. For a Weblog authored by a single
individual, it may be appropriate to omit the author element.
4.3.1.5 category Element
The category element, if present, MUST contain a string that
identifies a categorization for the item. It SHOULD use forward slash
delimitation to indicate hierarchy.
The category element MAY have a domain attribute, which MUST be a
string that identifies a categorization taxonomy.
The category element MAY be repeated to associate multiple
categorizations with an item.
4.3.1.6 comments Element
The comments element, if present, MUST be a URL, indicating a page
for comments relating to the item.
4.3.1.7 enclosure Element
The enclosure element, if present, describes a media object that is
logically attached to the item. It MUST have a url attribute, a
length attribute, and a type attribute.
The url attribute indicates the location of the enclosure; it MUST be
a http-schemed URL.
The length attribute indicates the size of the enclosure in bytes.
The type attribute indicates the media type of the enclosure.
4.3.1.8 guid Element
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The guid element, if present, MUST contain a string that uniquely
identifies the item. Commonly, the guid element is used to determine
whether an item is new, and to disambiguate it from other items.
The guid element MAY have a isPermaLink attribute, whose value MUST
be either "true" or "false". The isPermaLink attribute indicates
whether the guid also serves as a long-lived URL for the item. If the
isPermaLink attribute is not present, the default value is "true".
If the value of the isPermaLink attribute is "true", the contents of
the guid element MUST contain a URL that points to a Web page
described by the item element.
If the value of the isPermaLink attribute is "false", consumers of
RSS documents MUST consider the guid string as opaque.
4.3.1.9 pubDate Element
The pubDate element, if present, MUST be an RFC822-formatted [4] date
(subject to the caveats below) that indicates when the item was
published. If pubDate indicates a future date, consumers MAY choose
to ignore the item until that date has passed.
4.3.1.10 source Element
The source element, if present, MUST contain a string that indicates
the RSS channel that the item came from. It SHOULD be derived from
the channel's title.
The source element MUST have a url attribute, which MUST be a URL
indicating an XML source of the channel.
This element is designed to enable the propogation of credit for
items, and SHOULD be generated automatically by tools where
appropriate.
5. Date Formatting
RFC822-formatted dates in this specification MAY use two or four
digits to indicate a year; it is RECOMMENDED that four digits are
used.
6. Extending RSS
Elements and attributes MAY be introduced in the RSS format to extend
its functionality. Such extensions MUST use XML Namespaces [2] to
distinguish themselves from RSS elements as well as other extensions.
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7. IANA Considerations
To: ietf-types@iana.org
Subject: Registration of MIME media type application/rss+xml
MIME media type name: application
MIME subtype name: rss+xml
Required parameters: none
Optional parameters:
charset
Same as charset parameter of application/xml as specified in
RFC3023 [7].
revision
The optional revision parameter indicates the integer version of
RSS used; the value is specified by the target RSS version.
namespace
The optional namespace parameter indicates the XML namespace [2]
URI of the RSS format, if available.
Encoding considerations:
Same as encoding considerations of application/xml as specified in
RFC3023 [7].
8. Security Considerations
Like any Internet format, values in RSS documents should be examined
for invalid content, and careful care should be taken if it is to be
used as input to further processing (e.g., using a date value as the
basis of a calculation).
Furthermore, because HTML is a common payload of RSS files, careful
consideration should be given before excecuting content such as
ECMAScript or similar.
Additionally, the security considerations of RFC3023 [7] should be
taken into account when generating and processing RSS files.
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References
[1] Bray, T., Paoli, J., Sperberg-McQueen, C. and E. Maler,
"Extensible Markup Language (XML) 1.0 (Second Edition)", W3C REC
REC-xml-20001006, October 2000.
[2] Bray, T., Hollander, D. and A. Layman, "Namespaces in XML", W3C
REC REC-xml-names-19990114, January 1999.
[3] Krauskopf, T., Miller, J., Resnick, P. and W. Treese, "PICS 1.1
Label Distribution -- Label Syntax and Communication Protocols",
W3C REC REC-PICS-labels-961031, October 1996.
[4] Crocker, D., "Standard for the format of ARPA Internet text
messages", STD 11, RFC 822, August 1982.
[5] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[6] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource
Identifiers (URI): Generic Syntax", RFC 2396, August 1998.
[7] Murata, M., St. Laurent, S. and D. Kohn, "XML Media Types", RFC
3023, January 2001.
[8] Alvestrand, H., "Tags for the Identification of Languages", BCP
47, RFC 3066, January 2001.
[9] <http://backend.userland.com/rss>
[10] <http://www.thetwowayweb.com/soapmeetsrss>
Author's Address
Mark Nottingham
EMail: mnot@pobox.com
URI: http://www.mnot.net/
Appendix A. UserLand Copyright Statement
This work is derived from the RSS 2.0.1 specification, which requires
the following statement:
รจ Copyright 1997-2002 UserLand Software. All Rights Reserved.
This document and translations of it may be copied and furnished
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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 these paragraphs are included on all such copies and
derivative works.
This document may not be modified in any way, such as by removing
the copyright notice or references to UserLand or other
organizations. Further, while these copyright restrictions apply
to the written RSS specification, no claim of ownership is made by
UserLand to the format it describes. Any party may, for commercial
or non-commercial purposes, implement this format without royalty
or license fee to UserLand. The limited permissions granted herein
are perpetual and will not be revoked by UserLand or its
successors or assigns.
This document and the information contained herein is provided on
an "AS IS" basis and USERLAND 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.
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Intellectual Property Statement
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
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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.
Full Copyright Statement
Copyright (C) The Internet Society (2003). 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 assignees.
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
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HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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