There are a number of standards for supporting 'tags' in RSS including:
dc:subject RSS 2.0 'category' mod_taxonomy
How are we going to build a generic API that supports all systems currently in use?
Delicious=
<taxo:topics> <rdf:Bag> <rdf:li resource="http://del.icio.us/tag/programming"/> </rdf:Bag> </taxo:topics>