rdf interfaces

Hello

I've just had a first look at rdf interfaces
http://www.w3.org/TR/rdf-interfaces/.

While there are many very interesting aspects, there were two things which
I found rather irrirtating:

- That it deals with prefixes
- That it specifies how a blank node is to be stringified

Both aspects seem to be related to RDF serialization. I think it would be
usefull to have defined interfaces to deal with RDF on the level of
abstract syntax (and to a certain degree semantics) and have separate APIs
(or extensions) to deal with aspects of a concrete syntax.

Cheers,
Reto