If you are building an RSS parser, how important is it to build support for RDF?
Are any new feeds being published in only RDF?
My thinking was that RSS 2.0 (and Atom) have replaced RDF.
I actually had not heard of RDF until a client pointed out some feeds that are RDF-only.
RDF is a general data-storage format, not a web feed format. Are you thinking of some older version of RSS, which were RDF-based?
RSS 1.0, which is built around RDF, does still crop up from time to time, so you should built support for it (along with the other 8 versions of RSS, and the ability to recover from errors since many RSS feeds are invalid and not well formed). Better yet, use an existing RSS parser instead of reinventing the wheel.