comments on Web Services architecture requirements. ( D-AC009 )

I would like to get the background for the following requirements.  Source
of the requirements, reason for this requirement.


D-AC009 
is aligned with the semantic web initiative at W3C.

D-AR009.1 Any meta data about any aspect of the Web Services reference
architecture should be expressible with an RDF based language (such as RDF
itself, RDF Schema, DAML+OIL)

D-AR009.2 All recommendations produced by the working group include a
normative mapping between all XML technologies and RDF/XML.

D-AR009.3 All conceptual elements should be addressable directly via a URI
reference


Best Regards,
Sateesh