Re: To embed or combine

Dave Reynolds wrote:
> 
> Jos de Bruijn wrote:
>> Dave,
>>
>> I'm afraid I don't really see the difference between "accessing RDF
>> data" and "entailment regimes", so I don't really understand why they
>> should be treated differently.
> 
> I'm not suggesting they be treated differently.
> 
> To write rules that work with the data, or to implement a translator for
> those rules, the data mapping does have to normatively defined. To me
> this means that tr and the treatment of bNodes in data (not necessarily
> queries), literals etc have to all be normative. In the current document
> almost all of that is covered - literals are in the normative part, tr
> is implicit in the model theory but the handling of bNodes is not
> spelled out. Spelling tr out and defining the bNode handling in the
> normative part would resolve this, and would further increase the
> clarity of the document, at the trivial cost of moving a very small
> number of lines of text around.

I'm not sure what you mean with "spelling out tr". If you mean that we
need to show how using RDF data with RIF rules can be done, then it is
indeed something we still need to do, in the "Guide to using RIF with
the semantic web" document you mentioned.
The handling of bNodes is indeed not spelled out, because it is implicit
in the semantics.  They are symbols local to an RDF graph, so a
combination does not need to, and should not, touch these symbols.  We
do, however, need more explanatory text about this point.

So, with respect to the handling of blank nodes I think we are fine in
the normative part; we simply need more explanation in the informative part.

> 
>> Wouldn't one simply use a combination with the simple entailment regime
>> in this case?
> 
> Yes, I pointed this out in the "at first I was concerned" paragraph
> (since subset semantics includes the trivial subset).

I did not understand what is meant with "subset semantics".  Also, could
you send a pointer for rho-df?

Best, Jos

> 
> Dave

-- 
Jos de Bruijn            debruijn@inf.unibz.it
+390471016224         http://www.debruijn.net/
----------------------------------------------
The third-rate mind is only happy when it is
thinking with the majority. The second-rate
mind is only happy when it is thinking with
the minority. The first-rate mind is only
happy when it is thinking.
  - AA Milne