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

From: Jos de Bruijn <debruijn@inf.unibz.it>
Date: Wed, 24 Feb 2010 12:59:34 +0100
Message-ID: <4B8514A6.3080903@inf.unibz.it>
To: Axel Polleres <axel.polleres@deri.org>
CC: Sandro Hawke <sandro@w3.org>, Birte Glimm <birte.glimm@comlab.ox.ac.uk>, SPARQL Working Group <public-rdf-dawg@w3.org>


On 2010-02-24 12:53, Axel Polleres wrote:
> Note in that context that, another issue is the following:
> 
> RIF entailment is strictly speaking not only parametric to the
> dialect (Core/BLD/strongly safe core ... I hope we can define a
> unified entailmanet regime which catches all three) but also to the

The definition of entailment is the same for all three, so I don't see
why one would define different entailment regimes in the first place?

Jos

> combination semantics chosen, cf.
> http://www.w3.org/TR/rif-rdf-owl/#Profiles_of_Imports, i.e. do we
> want to define only a RIF/Simple-Entailment regime, or also:
> 
> RIF/RDF RIF/RDFS RIF/D RIF/OWL RIF/OWL DL RIF/OWL Full
> 
> (btw, the latter two have been renamed in the latest editor's draft
> in RIF, , cf.
> http://www.w3.org/2005/rules/wiki/SWC#Profiles_of_Imports, due to
> comments form the OWL WG to RIF/OWL Direct RIF/OWL RDF-Based )
> 
> To start with, I think my original proposal works straightforwardly
> for RIF/Simple, the others (particularly when we jump up to OWL) need
> more thought, and probably checking back with Jos & Birte ;-)
> 
> 
> Axel
> 
> 
> P.S.: <chairhat-off>I note that for my main use case, which is
> modeling different rule based approximations of fragments of the RDFS
> and OWL semantics in RIF, RIF/Simple is probably
> sufficient..</chairhat-off>
> 
> 
> On 24 Feb 2010, at 11:38, 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?
>> 
>> b) seems to be the most reasonable way to go; but make sure to
>> include at least one representative (for queries with blank
>> nodes). Unnecessarily ignoring parts of the semantics (as in a)
>> seems rather a bad idea.
>> 
>> 
>> Cheers, Jos
>> 
>>> 
>>> 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
>>>> 
>>> 
>> 
>> -- Jos de Bruijn Web:   http://www.debruijn.net/ Phone: +39 0471
>> 016224 Fax:   +39 0471 016009
>> 
> 

-- 
Jos de Bruijn
  Web:   http://www.debruijn.net/
  Phone: +39 0471 016224
  Fax:   +39 0471 016009
Received on Wednesday, 24 February 2010 11:59:24 GMT

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