RE: [SKOS, SPARQL, ALL] Closure and SPARQL

Perhaps a modified example from the people ontology might help to explain what I'm trying to say. Suppose we have the following graph:

HasPet subPropertyOf Likes
Person subClassOf Animal 
Woman subClassOf Person
OldLady subClassOf Woman
OldLady HasPet Cat
Cat subClassOf Animal

A query 
(X subClass Person) AND (X Likes Animal) 
gives the answer 
{X= OldLady}

This takes the class-hierachy into account, as wel as the property hierachy.

Unless I have I missed this somewhere, according to the specifications, the query on this graph would not give this result and the resultset would be empty. 

I would say "simple RDf entailment" and "RDF entailment" entailment as you point out in 2) should be possible on the same graph, but I got the impression that this is not possible.
1) can be resolved by doing a minus between the entailment and the simple entailment results. 

Hope this helps,
   Christoffel





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> -----Original Message-----
> From: Enrico Franconi [mailto:franconi@inf.unibz.it]
> Sent: maandag 12 december 2005 12:50
> To: Christoffel Dhaen
> Cc: McBride, Brian; David Wood; Pat Hayes; Christopher Welty; public-swbp-
> wg@w3.org
> Subject: Re: [SKOS, SPARQL, ALL] Closure and SPARQL
> 
> On 12 Dec 2005, at 11:49, Christoffel Dhaen wrote:
> > That’s all. RDF is a graph, it has native transitive properties.
> > Being able to express in query that only the direct nodes should be
> > taken into account, or that the transitive nature of the properties
> > has to be taken into account is a logical step. No more, no less.
> 
> At this point it is not clear to me anymore what you want :-)
> 
> 1) if you want, e.g., to ask for the "descendant" property if you
> have only the "child" property in the graph, then you need the
> abiltiy to express the transitive closure of a property in the query
> language. This has a cost, and current SPARQL does not handle this.
> 
> 2) if you want to distinguish in a query between "stated" transitive
> properties from "derived" transitive properties, then you need a
> different mechanism. This would be the case of existing transitive
> properties in RDFS; e.g., subClass: if there is a graph "(a subClass
> b)(b subClass c)" whenever you ask for "(X subClass c)" you want to
> get the answer "X=b" as being somehow directly stated as opposed to
> the answer "X=a" as being somehow derived. This distinction is
> possible according to the latest discussions in the DAWG: if you make
> the query "(X subClass c)" by requiring only "simple RDf entailment"
> you get the answer set {X=b}, while if you require "RDF entailment"
> you get the answer set {X=b, X=a}. "simple RDf entailment" and "RDf
> entailment" are defined in the RDF MT semantics W3C document.
> 
> Does this characterise your request?
> 
> cheers
> --e.
> 
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Received on Monday, 12 December 2005 14:24:31 UTC