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