In RSS 2.0, a provision is made for linking a channel to its identifier in a cataloging system, using the channel-level category feature. For example, to link a channel to its Syndic8 identifier, include a category element as a sub-element of channel, with domain "Syndic8", and value the identifier for your channel in the Syndic8 database. The appropriate category element for Scripting News would be 1765. Taken verbatim from http://blogs.law.harvard.edu/tech/rss.

Specifies a web service that supports the rssCloud interface which can be implemented in HTTP-POST, XML-RPC or SOAP 1.1. Its purpose is to allow processes to register with a cloud to be notified of updates to the channel, implementing a lightweight publish-subscribe protocol for RSS feeds. Taken verbatim from http://blogs.law.harvard.edu/tech/rss.

Describes a media object that is attached to the item. Taken verbatim from http://blogs.law.harvard.edu/tech/rss.

guid stands for globally unique identifier. It's a string that uniquely identifies the item. When present, an aggregator may choose to use this string to determine if an item is new. Taken verbatim from http://blogs.law.harvard.edu/tech/rss.

Specifies a GIF, JPEG or PNG image that can be displayed with the channel. Taken verbatim from http://blogs.law.harvard.edu/tech/rss.

Its value is the name of the RSS channel that the item came from, derived from its title. It has one required attribute, url, which links to the XMLization of the source. Taken verbatim from http://blogs.law.harvard.edu/tech/rss.

The purpose of the textInput element is something of a mystery. You can use it to specify a search engine box. Or to allow a reader to provide feedback. Most aggregators ignore it. Taken verbatim from http://blogs.law.harvard.edu/tech/rss.