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Re: [RIF: SWC] SPARQL and RIF

From: Ed Barkmeyer <edbark@nist.gov>
Date: Fri, 27 Jan 2006 13:38:48 -0500
Message-ID: <43DA68B8.3060908@nist.gov>
To: Enrico Franconi <franconi@inf.unibz.it>
CC: W3C RIF WG <public-rif-wg@w3.org>

Enrico Franconi wrote:

>  From the minutes: [first draft]
> (...)
> 
>> Edward Barkmeyer: conclusions in rule heads might not be compatible  
>> with RDF model.
> 
> What do you mean here?

Francois corrected this to:
   Edward Barkmeyer: SPARQL inferences in rule heads may not be compatible with
the RIF model.

What I had in mind was closer to what Axel said:

>> Axel Polleres: hmmm, if we allow SPARQL (or any other query language) 
>> in the body and the query is recursively dependent on the rule 
>> consequent... we are gonna run into some issues

If the result from a SPARQL query required an inference, then the SPARQL 
interpretation requires RDF-compatible semantics, but the RIF KB is not 
necessarily, or even probably, monotonic.  The RDF semantics will treat 
"currently true" as "always true", which can lead to unsafe conclusions over 
an RDF ontology that is otherwise safe.  We would need to guard RIF "facts" 
whose interpretation under the (monotonic) RDF ontology is unsafe.  The 
problem is generally restricted to the recording of "current rules-based 
inferences" as "facts" in the RIF KB (in order to trigger other rules), when 
the rules-based inference may have involved negation-as-failure.  The RIF 
"fact" is not an RDF "fact".

(That is what I meant.  I accept that it may be "under-educated". :-) )

As (I think) ChrisW later said, the real underlying issue is the relationship 
of the RIF Ruleset to the RDF ontology.

-Ed

-- 
Edward J. Barkmeyer                        Email: edbark@nist.gov
National Institute of Standards & Technology
Manufacturing Systems Integration Division
100 Bureau Drive, Stop 8263                Tel: +1 301-975-3528
Gaithersburg, MD 20899-8263                FAX: +1 301-975-4482

"The opinions expressed above do not reflect consensus of NIST,
  and have not been reviewed by any Government authority."
Received on Friday, 27 January 2006 18:38:59 GMT

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