[RIF-RDF] update of RDF compatibility section

Dear all,

I've done a major update of the RDF compatibility section [1].

- All discussions around RDF compatibility have been taken into account
in this version.  Discussion issues which remain open, as well as new
discussion issues which I've uncovered, are now clearly marked using a
blue background in the document.
- Many explanations and resolutions of earlier issues are now marked as
comments, using a green background in the document.
- I have improved the layout, making it more readable.
- The section on the "minimal subset" has been moved to the RDF section
in an architecture document [2], which I currently consider a parking
lot for RDF-related issues (most of the content on the page is somewhat
outdated).
- The definition of the semantics of combinations has been simplified
considerably.  The semantics of the combination is now given through a
combination of an RIF semantic structure and an RDF interpretation,
rather than the definition of a corresponding RDF interpretation; the
interaction between the two is defined through a number of conditions on
interpretations. Furthermore, the same definition of interpretations is
used for all entailment regimes. I believe this simplification might
address some of the concerns about the complexity of the proposal [in
fact, in length, the definition of the semantics of combinations is no
shorter than the definition of the embeddings].
- The definition of the embeddings has been updated to reflect the
semantics of datatypes in RIF.

I hope this update is in time for the description in the telephone
conference tomorrow.

Later today, I will send a more detailed rationale (than the one
provided in [3]) for the definition of combinations in [1].


Best, Jos

[1] http://www.w3.org/2005/rules/wg/wiki/Core/RIF-RDF_Compatibility
[2] http://www.w3.org/2005/rules/wg/wiki/Arch/RDF
-- 
Jos de Bruijn            debruijn@inf.unibz.it
                      http://www.debruijn.net/
----------------------------------------------
As far as the laws of mathematics refer to
reality, they are not certain; and as far as
they are certain, they do not refer to
reality.
  -- Albert Einstein