Re: rdf as a base for other languages

   [Brian McBride]
   Can you point me to an explanation as to why extending RDF is the better
   approach?  Why is it necessary or better that RDF be a sub-language of LL?

At the risk of repeating what others have said, here is my
explanation:

The case you are thinking of is something like this: There is a
statement P, expressed in RDF, and a rule, P=>Q, expressed in some
other language, such that an inference engine, looking at the two,
could infer Q, a purely RDF conclusion.

Unfortunately, not all rules operate purely on conjunctions.  E.g.,

    (or P Q), (not Q) => P

So we still have to come up with a way of representing complex
formulas, which requires extending RDF.

                                             -- Drew McDermott