Network Working Group J. Snell
Internet-Draft September 9, 2005
Expires: March 13, 2006
Feed Index: Enabling Ordered Entries in Atom
draft-snell-atompub-feed-index-02.txt
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This memo presents a mechanism that allows feed publishers to
establish a numeric sorting index for the entries contained within a
feed.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Notational Conventions . . . . . . . . . . . . . . . . . . . . 3
3. The 'i:ordered' Element . . . . . . . . . . . . . . . . . . . 3
4. Presenting Ordering Entries . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 5
Intellectual Property and Copyright Statements . . . . . . . . 7
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1. Introduction
In syndication document formats such as Atom [I-D.ietf-atompub-
format] and RSS ([http://purl.org/rss/1.0/spec][http://
blogs.law.harvard.edu/tech/rss]), the order of entries as presented
in the list is typically insignificant. This presents a challenge
when the list of entries is intended to represent an ordered list of
elements. This document specifies a mechanism that allows feed
publishers to indicate whether or not the order of entries within a
feed is should be considered to be significant. Although it refers
to Atom normatively, the mechanism described herein can be used with
similar syndication formats, such as the various flavors of RSS.
2. Notational 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 BCP 14, [RFC2119], as
scoped to those conformance targets.
In this specification, "entry" refers to an atom:entry element or
similar construct from other syndication formats (e.g., RSS) that are
contained within a feed.
In this specification, "feed" refers to an Atom Feed Document or
similar syndication format (e.g., RSS) that contains a collection of
entries.
In this specification, "head section" refers to the children of a
feed document's document-wide metadata container; e.g., the child
elements of the atom:feed element in an Atom Feed Document.
This specification uses XML Namespaces [W3C.REC-xml-names-19990114]
to uniquely identify XML element names. It uses the following
namespace prefix for the indicated namespace URI;
"i": "http://purl.org/syndication/index/1.0"
This specification uses terms from the XML Infoset [W3C.REC-xml-
infoset-20040204]. However, this specification uses a shorthand; the
phrase "Information Item" is omitted when naming Element Information
Items. Therefore, when this specification uses the term "element,"
it is referring to an Element Information Item in Infoset terms.
3. The 'i:ordered' Element
The i:ordered element is used to indicate that the order of entries
within a feed SHOULD be considered significant. It MUST NOT occur
more than once in a feed's head section. The element's value MUST be
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empty.
For example,
The i:ordered element MAY have a sort attribute whose value indicates
the default sort order of entries. The attribute's value MUST be
either "descending" indicating a last-to-first sort order or
"ascending" indicating an first-to-last sort order. If the sort
attribute is omitted, a value of "ascending" is assumed. The value
of the sort attribute is case insensitive.
For example,
The i:ordered element MUST NOT contain any other attributes.
4. Presenting Ordering Entries
When presented with a feed whose head section contains an i:ordered
element, a consumer MAY present the entries in either an ascending or
descending order based on the position of the entry within the feed
and the value of the i:ordered element's sort attribute if present
(ascending order if not).
For example,
...
tag:entry:1
...
tag:entry:2
...
tag:entry:3
...
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When presented, the entries from the example feed SHOULD be
displayed, by default, in descending order:
1. tag:entry:3
2. tag:entry:2
3. tag:entry:1
Consumers are not required to present entries in the order
established by the i:ordered element.
5. Security Considerations
There are no security considerations introduced by this
specification.
6. References
[I-D.ietf-atompub-format]
Sayre, R. and M. Nottingham, "The Atom Syndication
Format", draft-ietf-atompub-format-11 (work in progress),
August 2005.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[W3C.REC-xml-infoset-20040204]
Tobin, R. and J. Cowan, "XML Information Set (Second
Edition)", W3C REC REC-xml-infoset-20040204,
February 2004.
[W3C.REC-xml-names-19990114]
Hollander, D., Bray, T., and A. Layman, "Namespaces in
XML", W3C REC REC-xml-names-19990114, January 1999.
[W3C.REC-xmlschema-2-20041028]
Malhotra, A. and P. Biron, "XML Schema Part 2: Datatypes
Second Edition", W3C REC REC-xmlschema-2-20041028,
October 2004.
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Author's Address
James M Snell
Phone:
Email: jasnell@gmail.com
URI: http://snellspace.com
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