Developing Feeds with RSS and Atom

Namespaces and Modules Within RSS 2.0 and Atom

As mentioned earlier, RSS 2.0 introduced namespaced modules to the simple strand of RSS. RSS 1.0 was designed with namespace support from the very beginning. The specification document states:

A RSS feed may contain elements not described on this page, only if those elements are defined in a namespace. The elements defined in this document aren’t themselves members of a namespace, so that RSS 2.0 can remain compatible with previous versions in the following sense—a version 0.91 or 0.92 file is also a valid 2.0 file. If the elements of RSS 2.0 were in a namespace, this constraint would break, a version 0.9x file would not be a valid 2.0 file.

Other than not defining a namespace for the core elements of RSS 2.0, the modules work the same way as the modules for RSS 1.0: declare the module’s namespace in the root element (which in the case of RSS 2.0 is, of course, rss) and then use the module elements as directed by their specification. Parsers that don’t recognize the namespace just ignore the new elements.

Differences from RSS 1.0

RSS 1.0 modules can’t be reused within RSS 2.0. To do so requires the feed author to declare two additional namespaces within the root element: the namespace of the module and the namespace of RDF. This isn’t explicitly forbidden but is heavily frowned upon.

Because of this, you need to recall the simplest ways to convert between the default module styles. RSS 1.0 modules, you will remember, declare everything ...