A typical namespace declaration for the blogChannel namespace (Christian web host)
A typical namespace declaration for the blogChannel namespace is: xmlns:blogChannel= http://backend.userland.com/blogChannelModule The following elements are in the blogChannel module: . blink: This contains a URL that links to a blog that the author of the information feed wants to promote in some way. . blogRoll: This contains a URL that specifies the location of an OPML (Outline Processor Markup Language) file containing the blogroll for the information feed. . changes: This contains a URL that specifies the location of a changes.xml file. The idea behind the changes file is that bandwidth use may be reduced. . mySubscriptions: This contains a URL that specifies the location of an OPML file containing the subscriptions of the blog author. Whether or not an extension module is supported can vary from one aggregator tool to another. A quasi-official list of RSS 2.0 extensions is maintained at http://blogs.law.harvard.edu/tech/ directory/5/specifications/rss20ModulesNamespaces. Examples include Danny Ayer s Simple Semantic Resolution module and Joe Gregorio s Comment API. Summary RSS 2.0 adds the use of XML namespaces to the document structure of RSS 0.9x. It does not use the RDF. New elements add information about the software creating the feed, the author of the feed, and the location of a comments page for the information feed (a facility used primarily when the information feed relates to a blog). In this chapter you learned that: . RSS 2.0 uses XML namespaces. . The document element of an RSS 2.0 document is the rss element. . All information in an RSS 2.0 information feed is contained in the channel element. . Information feed items are contained in item elements. OPML, Outline Processor Markup Language, is an XML language that can express the structure of an outline. In the context of information feeds, an OPML document is often used to contain a list of information feeds to which a blogger subscribes, the so-called blogroll. 128 Chapter 12