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Re: Final text for Basic Graph Patterns

From: Enrico Franconi <franconi@inf.unibz.it>
Date: Wed, 18 Jan 2006 15:27:18 +0100
Message-Id: <DE921816-BEFB-4961-81B5-2CAFB9810209@inf.unibz.it>
Cc: Dan Connolly <connolly@w3.org>, Pat Hayes <phayes@ihmc.us>, RDF Data Access Working Group <public-rdf-dawg@w3.org>
To: Bijan Parsia <bparsia@isr.umd.edu>


On 18 Jan 2006, at 15:11, Bijan Parsia wrote:
>
> On Jan 18, 2006, at 5:55 AM, Enrico Franconi wrote:
>
>> On 18 Jan 2006, at 04:58, Pat Hayes wrote:
> [snip]
>>> I am still bothered by the possibilities of OWL-specific notions  
>>> of redundancy in answer sets. Consider an OWL/RDF KB that asserts
>>>
>>> :a rdf:type :A
>>> :a rdf:type :B
>>> :a rdf:type :C
>>> :A rdf:type owl:Class
>>> :B rdf:type owl:Class
>>> :C rdf:type owl:Class
>>>
>>> and an OWL query
>>>
>>> SELECT ?x WHERE {:a rdf:type ?x .}
> [snip]
>>> Now, this dataset OWL-entails the *existence* of a triple  
>>> intersection and three double intersections, all with :a in them.  
>>> So are these reasonable answer bindings for such a query? I see  
>>> no good reason why they should not be:
> [snip]
>
> How about all the disjunctions involving them? (Or all disjunctions  
> rooted in them?) Or all min 0 restricitons?
>
> It's very very very tricky. I've been thinking about such queries  
> and the obvious (first step) restrictions to the binding of ?x are  
> URIs and explicit/told bnodes (for cases where someone has made an  
> type assertion to an anonymous class). I tend to think that fishing  
> expeditions of this sort are just going to die hard.

I agree.

> (Syntactically there's a fairly sever problem, IMHO, in that you  
> can't current return an expression as a binding. So you'd have to  
> rely on bnode stability in more contexts.)
>
> Retrieving the named types + forcing the user to speculate about  
> complex expressions, or maybe adding asserted complex expressions  
> seems to be at the limit of what we know how to do reasonably well  
> (from an interface standpoint) and the former is all I've seen  
> implemented or proposed.

I agree. And if UMD agrees, since they are OWL-full experts and  
supporters, then we are in safe hands.

cheers
--e.
Received on Wednesday, 18 January 2006 14:27:35 GMT

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