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Re: finite approximation of the minimal Herbrand model for a RIF Core/BLD ruleset.

From: Axel Polleres <axel.polleres@deri.org>
Date: Wed, 24 Feb 2010 11:32:21 +0000
Cc: "Sandro Hawke" <sandro@w3.org>, "Birte Glimm" <birte.glimm@comlab.ox.ac.uk>, "SPARQL Working Group" <public-rdf-dawg@w3.org>
Message-Id: <F3E37CA8-BA84-4BF2-B471-949DA3B5E893@deri.org>
To: "Jos de Bruijn" <debruijn@inf.unibz.it>

On 24 Feb 2010, at 11:28, Jos de Bruijn wrote:

> 
> 
> On 2010-02-24 12:24, Axel Polleres wrote:
> > Below I forward some thought from jos on this with his consent:
> >
> > @jos: can you ealborate what exactly you mean here:
> >
> >> 2- the RDF(S) semantics gives you more than just blank nodes.
> >
> > in how far is this a (potential) problem?
> 
> I'm not saying this is a problem per se. You were simply not taking the
> RDF(S) semantics (i.e., axiomatic triples & semantics conditions) into
> account in the definition you proposed.

yes, this is another issue. good point. 

> Of course one needs to be careful with the infinite axiomatic triples,
> especially when considering query answering and not just checking
> entailment.

A common way to deal with this in a finite approximation way is 
a) ignoring (specifically the infinite) axiomatic triples alltogether 
b) take only those from the infinite axiomatic triples (those about container membership properties)
that appear in the graph... I believe the latter is what we do in the current RDF(S) entailment regime, yes Birte?

Axel

> 
> 
> Jos
> 
> >
> > Axel
> >
> >
> >> ============================================================================
> >> On 2010-02-24 12:07, Axel Polleres wrote:
> >>>
> >>> On 24 Feb 2010, at 11:04, Jos de Bruijn wrote:
> >>>> On 2010-02-24 11:28, Axel Polleres wrote:
> >>>>> Hi Jos,
> >>>>>
> >>>>> Can you check this briefly and tell me whether I don't oversimplify
> >>>>> things here?
> >>>>
> >>>> I will have a more detailed look at it later on, but a few first comments:
> >>>> - you do not consider equality between data values, e.g.
> >>>> "1"^^int="1"^^decimal
> >>>
> >>> hmmm, I am at the moment, not sure how far this is a problem, but I definitly should include this in the issues!
> >>>
> >>>
> >>>> - I did not see how a minimal model for RIF-RDF combinations is defined,
> >>>> in particular I see no blank nodes or RDF(S) semantics
> >>>
> >>> ? Can't we just treat them as skolem constants? We are just interested in query answering...
> >>
> >> 1- if you treat blank nodes as skolem constants you need to say so.
> >> 2- the RDF(S) semantics gives you more than just blank nodes.
> >>
> >>> if you agree, I forward your comments to SPARQL, ok?
> >>
> >> Sure.
> >>
> >>
> >> Jos
> >
> >
> 
> --
> Jos de Bruijn
>   Web:   http://www.debruijn.net/
>   Phone: +39 0471 016224
>   Fax:   +39 0471 016009
> 
Received on Wednesday, 24 February 2010 11:32:55 GMT

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