RSS 2.0 Specification(RSS 2.0 参考 ) 转自:http://blogs.law.harvard.edu/tech/rss

Really Simple Syndication

RSS Advisory Board announcements and RSS news

RSS 2.0 Specification

Contents

• What is RSS?
• Sample files
• About this document
• Required channel elements
• Optional channel elements
• Elements of
• Comments
• Extending RSS
• Roadmap
• License and authorship

What is RSS? 

RSS Directory

	About this website
	Specifications
	Feeds
	Aggregators
	Validators
	Howtos/Articles
	Tools
	Utilities

RSS is a Web content syndication format.

Its name is an acronym for Really Simple Syndication.

RSS is a dialect of XML. All RSS files must conform to the XML 1.0 specification, as published on the World Wide Web Consortium (W3C) website.

A summary of RSS version history.

At the top level, a RSS document is a element, with a mandatory attribute called version, that specifies the version of RSS that the document conforms to. If it conforms to this specification, the version attribute must be 2.0.

Subordinate to the element is a single element, which contains information about the channel (metadata) and its contents.

Sample files 

Here are sample files for: RSS 0.91, 0.92 and 2.0.

Note that the sample files may point to documents and services that no longer exist. The 0.91 sample was created when the 0.91 docs were written. Maintaining a trail of samples seems like a good idea.

About this document 

This document represents the status of RSS as of the Fall of 2002, version 2.0.1.

It incorporates all changes and additions, starting with the basic spec for RSS 0.91 (June 2000) and includes new features introduced in RSS 0.92 (December 2000) and RSS 0.94 (August 2002).

Change notes are here.

First we document the required and optional sub-elements of ; and then document the sub-elements of . The final sections answer frequently asked questions, and provide a roadmap for future evolution, and guidelines for extending RSS.

Required channel elements 

Here's a list of the required channel elements, each with a brief description, an example, and where available, a pointer to a more complete description.

Element	Description	Example
title	The name of the channel. It's how people refer to your service. If you have an HTML website that contains the same information as your RSS file, the title of your channel should be the same as the title of your website.	GoUpstate.com News Headlines
link	The URL to the HTML website corresponding to the channel.	http://www.goupstate.com/
description	Phrase or sentence describing the channel.	The latest news from GoUpstate.com, a Spartanburg Herald-Journal Web site.

Optional channel elements 

Here's a list of optional channel elements.

Element	Description	Example
language	The language the channel is written in. This allows aggregators to group all Italian language sites, for example, on a single page. A list of allowable values for this element, as provided by Netscape, is here. You may also use values defined by the W3C.	en-us
copyright	Copyright notice for content in the channel.	Copyright 2002, Spartanburg Herald-Journal
managingEditor	Email address for person responsible for editorial content.	geo@herald.com (George Matesky)
webMaster	Email address for person responsible for technical issues relating to channel.	betty@herald.com (Betty Guernsey)
pubDate	The publication date for the content in the channel. 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. All date-times in RSS conform to the Date and Time Specification of RFC 822, with the exception that the year may be expressed with two characters or four characters (four preferred).	Sat, 07 Sep 2002 00:00:01 GMT
lastBuildDate	The last time the content of the channel changed.	Sat, 07 Sep 2002 09:42:31 GMT
category	Specify one or more categories that the channel belongs to. Follows the same rules as the -level category element. More info.	Newspapers
generator	A string indicating the program used to generate the channel.	MightyInHouse Content System v2.3
docs	A URL that points to the documentation for the format used in the RSS file. It's probably a pointer to this page. It's for people who might stumble across an RSS file on a Web server 25 years from now and wonder what it is.	http://blogs.law.harvard.edu/tech/rss
cloud	Allows processes to register with a cloud to be notified of updates to the channel, implementing a lightweight publish-subscribe protocol for RSS feeds. More info here.
ttl	ttl stands for time to live. It's a number of minutes that indicates how long a channel can be cached before refreshing from the source. More info here.	60
image	Specifies a GIF, JPEG or PNG image that can be displayed with the channel. More info here.
rating	The PICS rating for the channel.
textInput	Specifies a text input box that can be displayed with the channel. More info here.
skipHours	A hint for aggregators telling them which hours they can skip. More info here.
skipDays	A hint for aggregators telling them which days they can skip. More info here.

sub-element of  

is an optional sub-element of , which contains three required and three optional sub-elements.

is the URL of a GIF, JPEG or PNG image that represents the channel.