RFC2533, etc.

Two good documents re rules, syntax, and matching:

Network Working Group                                         G. Klyne
Request for Comments: 2533                    Content Technologies/5GM
Category: Standards Track                                   March 1999

               A Syntax for Describing Media Feature Sets
http://www.ics.uci.edu/pub/ietf/http/rfc2533.txt 


"An algebra for describing media feature sets",
G. Klyne, 07 Aug 1998. 
http://www.ics.uci.edu/pub/ietf/http/draft-ietf-conneg-feature-algebra-03.txt

Hilarie