RSS

The emergence and growth of RSS, RSS standards, benefits of RSS services, and the RSS 2.0 Specification
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Overview

RSS is a format for distributing a brief summary of a website’s title or contents. It is mainly used to publish update information.

It is generally used to distribute blog update information, but it is also often used by news sites and TV schedule sites to distribute new article or program information, and by companies to distribute product information.

The term RSS is also referred to by the following names.

  • RDF Site Summary
    • RDF stands for Resource Description Framework, meaning a tool for writing metadata.
    • In other words, it is an agreement to “write this kind of information in this kind of form.”
  • Really Simple Syndication
    • Very simple distribution
  • Rich Site Summary
    • Rich site summary information

Emergence and Growth of RSS

The first development of RSS began from a concept at NetCenter, Netscape’s Internet portal site. Netscape was famous for its browser, and RSS was devised to provide articles from well-known newspapers easily.

Looking briefly at Netscape’s development history, the RSS format started from MCF (Meta Content Framework) in 1995, passed through the development of RDF (Resource Description Framework) and CDF (Channel Definition Format), and appeared as RSS (RDF Site Summary). However, Netscape abandoned further development after RSS 0.9. After that, two development groups formed and continued development, which is why RSS came to have two names.

RSS Standards

RSS (RDF Site Summary) 1.0 from the RSS-DEV Working Group and RSS (Really Simple Syndication) 2.0 from UserLand are industry standards.
The two specifications have slight functional differences, but UserLand’s 2.0 provides more detailed functions.

  • RSS 1.*: specifications based on RDF
    • RSS 0.9
    • RSS 1.0
    • RSS 1.1 (January 2005)
  • RSS 2.0: specifications not based on RDF
    • RSS 0.91
    • RSS 0.92
    • RSS 0.93
    • RSS 0.94
    • RSS 2.01

Other formats also appeared, such as Media RSS announced by Yahoo in December 2004, and around the end of 2004, methods of extending RSS formats and applying them to podcasting also appeared.

With the spread of RSS, recognition of the importance of content syndication, new functions, and the need for standardization grew. Many discussions and efforts for content syndication standardization took place, but it became difficult to unify and standardize RSS specifications, and this led to a new standardization project named Atom.

RSS continues to evolve. Although there are slight differences in methods, RSS is becoming established on the Internet because it develops based on the basic philosophy of being “open.”

Benefits of RSS Services

RSS has the following advantages.

  • Selective subscription
    • Users can choose channels that exactly match the topics they want.
  • Fast subscription
    • Multiple channel sources can be accessed at the same time.
  • History management
    • Past records from various channels can be stored.
  • Easy automated content integration
    • syndication / aggregation
  • Content reusability
    • Structured XML data can be easily transformed and processed.
  • Change in communication method
    • From one-to-one to one-to-many simultaneous access

RSS 2.0 Specification

0. <rss> Element

<rss version="2.0">
</rss>
  • A document complying with RSS 2.0 must have an element named rss as the document element.
  • The <rss> element must have the version attribute, and its value is always "2.0".
  • The <rss> element has the <channel> element as a child.

1. <channel> Element

The channel corresponds to a website. It has three required child elements and fifteen optional child elements.

Required Channel Elements

  • <title>: the name of the channel. Usually the same as the website name.
  • <link>: the address of the website that supplies this RSS.
  • <description>: promotional text that introduces or describes this channel (website).

Optional Channel Elements

  • <language>: specifies the main language of the channel according to ISO 639.
  • <copyright>: contains copyright text.
  • <managingEditor>: e-mail address of the post editor.
  • <webMaster>: e-mail address of the site administrator.
  • <pubDate>: publication date and time of this RSS, in RFC 822 format.
  • <lastBuildDate>: last modification time of posts in this channel, also in RFC 822 format.
  • <category>: topic or category of the channel.
  • <generator>: software used to publish this RSS.
  • <docs>: address where this RSS can be received.
  • <cloud>: node specifying RSS Cloud features such as real-time notification and opinion exchange.
  • <ttl>: limits how long the feed can be cached before it is fetched again.
  • <image>: specifies an image such as a logo representing the channel.
  • <textInput>: specifies a text box that can be displayed in the channel, often for search or feedback.
  • <skipHours>: specifies hours from 0 to 23 when RSS collectors should not fetch.
  • <skipDays>: specifies days when RSS collectors should not fetch.

<item> Element

The <item> element represents a post in the channel. It has required elements and optional elements.

  • <title>: title of the post.
  • <link>: URL of the post.
  • <description>: body of the post or part of the body.
  • <author>: e-mail address of the post author.
  • <category>: category to which the post belongs.
  • <comments>: address where comments for the post can be read.
  • <enclosure>: node for attached files, with url, length, and type attributes.
  • <guid>: a unique string that can programmatically identify only this post.
  • <pubDate>: date when the post was registered.
  • <source>: if the post came from another RSS feed, indicates that feed’s name and address.

Example RSS Written in RSS 2.0

<?xml version="1.0" encoding="utf-8"?>
<rss version="2.0">
   <channel>
      <title>Liftoff News</title>
      <link>http://liftoff.msfc.nasa.gov/</link>
      <description>Liftoff to Space Exploration.</description>
      <language>en-us</language>
      <pubDate>Tue, 10 Jun 2003 04:00:00 GMT</pubDate>
      <lastBuildDate>Tue, 10 Jun 2003 09:41:01 GMT</lastBuildDate>
      <docs>http://blogs.law.harvard.edu/tech/rss</docs>
      <generator>Weblog Editor 2.0</generator>
      <managingEditor>editor@example.com</managingEditor>
      <webMaster>webmaster@example.com</webMaster>
      <item>
         <title>Star City</title>
         <link>http://liftoff.msfc.nasa.gov/news/2003/news-starcity.asp</link>
         <description>How do Americans get ready to work with Russians aboard the International Space Station?</description>
         <pubDate>Tue, 03 Jun 2003 09:39:21 GMT</pubDate>
         <guid>http://liftoff.msfc.nasa.gov/2003/06/03.html#item573</guid>
      </item>
   </channel>
</rss>

References