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Re: [ENT] Review comments on the SPARQL 1.1. Entailment regime document

From: Ivan Herman <ivan@w3.org>
Date: Fri, 14 May 2010 10:15:45 +0200
Cc: Chimezie Ogbuji <ogbujic@ccf.org>, Axel Polleres <axel.polleres@deri.org>, Sandro Hawke <sandro@w3.org>, W3C SPARQL WG <public-rdf-dawg@w3.org>
Message-Id: <C91B567B-F918-4F59-A615-CC4A870DDFC0@w3.org>
To: Birte Glimm <birte.glimm@comlab.ox.ac.uk>
Hey Birte

unfortunately, some more (minor!) comments below


On May 13, 2010, at 22:07 , Birte Glimm wrote:

> 
>> -----------
>> Question/comment on Section 6.6.2
>> 
>> I think I would also add some more explanation to the sentence 'Without C2 one would...'.
> 
>> My understanding is that a pure inference would generate a possible values for ?x going through all possible datatypes with their combination with facets, which would then generate an infinite number of those. But C2 restricts that to those appearing explicitly in the vocabulary. If I am mistaken, that would still include ?x/xsd:date, ?x/xsd:NMTOKEN, etc, right? Ie, this select will return a whole bunch of things...
> 
> Actually there was a mistake in the example. I now have to examples
> with a bit more explanation. One example where the variable binds to
> literals, which can cause infinite bindings and another example, where
> the variable binds to datatypes such as xsd:integer etc.  In the later
> case there are only finitely many bindings since bindings are only to
> atomic values (IRIs, literals, bnodes) and complex ranges composed by
> restricting an existing datatype with facets cannot be used as
> binding.
> The whole section was moved up to the RDF-Based Semantics regime and
> is now in Sec. 5.1.
> 

I am o.k. with the content but not being moved into 5.1. The whole section refers to OWL, uses the functional syntax, etc, etc, ie, it belongs to the OWL section.

Of course... I guess the issue is that the content is also valid for the RDF based semantics of OWL and not only to DL. So the right place would be to place it there, instead of the OWL DL. The only caveat is that the functional syntax is still DL specific. A solution would be to remove the FSS expressions altogether (sorry...) and then place it to the OWL Full part.

> 
> [snip a RIF comment]
> 
>> -----------
>> Section 7.1
>> 
>> I also have an issue with the way rif:imports is defined. The text says that the _Graph_ should contain the predicate rdf:imports. This means, if my understanding is correct, that I cannot use that in the query, ie, I cannot have a query that says
>> 
>> SELECT *
>> WHERE {
>>   [] rdf:imports <...pathtoruleset...>
>>   ... all kinds of patterns
>> }
>> 
>> In other words, I cannot dynamically assign rule sets to the dataset. For a user this looks like a serious restriction because that means that the dataset provider dictates the rule sets it has, rather than the user.
>> 
>> Isn't it possible to say that the rdf:imports can also be part of the BGP and has, well, the same semantics of referring to a rule set?
>> 
>> Actually, the same question applies to various OWL regimes, too. Can I have a [] owl:imports <...> in my BGP? Should we allow this?
> 
> I think we have discussed this already before and the BGP is really
> not the place where these things should go IMO. A BGP just tests
> something, either whether the triples match to the queried graph or
> whether they are entailed by the queried graph. Even if you have a BGP
> such as
> { [] owl:imports ?x }
> the only natural interpretation is to consider that as a query that
> asks whether the queried graph contains an import statement. In OWL
> RDF-Based Semantics, you would get the IRIs of the imported ontologies
> back because these triples are just normal triples under RDF-Based
> Semantics. Under Direct Semantics you wouldn't get an answer because
> such triples are non-logical and not entailed no matter which binding
> you try.
> 
> What you can do in any regime is to create a new default graph that
> contains the triples from all documents in the FROM part of the query.
> E.g.,
> SELECT ?x FROM IRI_1, IRI_2 WHERE { ?x ex:p ex:o }
> uses the triples from both IRI_1 and IRI_2 to find the answers with
> whatever ent. reg. is being used.

Ah! Right. I think this is, technically, a way to go.

Maybe an example for that somewhere in the text would help idiots like me...

Thanks!

Ivan



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Received on Friday, 14 May 2010 08:15:34 GMT

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