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Re: Final text for Basic Graph Patterns

From: Bijan Parsia <bparsia@isr.umd.edu>
Date: Wed, 18 Jan 2006 09:11:52 -0500
Message-Id: <50681938e78483f5425ebec04928d471@isr.umd.edu>
Cc: Dan Connolly <connolly@w3.org>, Pat Hayes <phayes@ihmc.us>, RDF Data Access Working Group <public-rdf-dawg@w3.org>
To: Enrico Franconi <franconi@inf.unibz.it>

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.

(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.

Cheers,
Bijan.
Received on Wednesday, 18 January 2006 14:11:57 GMT

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