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Re: Comments on SPARQL 1.1 Property Paths

From: Douglas Reid <dreid@bbn.com>
Date: Tue, 2 Nov 2010 08:42:29 -0400
Cc: public-rdf-dawg-comments@w3.org
Message-Id: <36AD95BB-9971-4B57-8BCD-57578DB2FE22@bbn.com>
To: Andy Seaborne <andy.seaborne@epimorphics.com>
Andy (and the SPARQL working group),

I'm happy to acknowledge that my comment has been answered.

Thanks for listening,
Doug.

On Nov 2, 2010, at 5:34 AM, Andy Seaborne wrote:

> > Has there been any consideration of enabling, for lack of a better term, negated properties in property paths?  By negated properties, I mean the notion of "any property EXCEPTING x".  The use case that comes to mind is the notion of determining if two entities are connected via some graph pattern, without having to know how they are connected and wanting to ignore trivial / useless connections.   For instance, I might want to discover whether or not ex:GeorgeWBush and ex:TonyBlair have a connection in the graph, ignoring the fact that they are both (rdf:type ex:Politician)s.
> 
> Doug,
> 
> Sorry for the delay in replying. The property path material has been incorporated into the main query specification and now includes "Negated property sets" which matches the feature you suggested.
> 
> http://www.w3.org/TR/sparql11-query/#propertypaths
> 
> >
> > It seems that having a negation mechanism might be more efficient, in certain cases, than a long listing of alternatives.
> >
> > Consider:
> >
> > {
> >   ?x ( foaf:knows | ex:meetOnce | ex:workedWith | ex:ownedCompany | ex:employed | .. )* ?y .
> > }
> >
> > as compared to:
> >
> > {
> >   ?x  !( rdf:type | ^rdf:type)* ?y .
> > }
> 
> > Somewhat related question:  I think I understand why the WG doesn't want to tackle variable property paths, but might it be useful to include a mechanism for general property description, without explicit property naming?  One wouldn't need the chosen property for the path returned just be able to ontologically-describe an appropriate property to chose when considering paths.
> >
> > For instance, imagine trying to ensure, without exhaustive specification, that all property paths identified only occur through non-literal objects, so as to avoid trivial connections (say ex:first_name or ex:age).
> >
> > It might look something like:
> >
> > {
> >    ?x  ( [ a owl:ObjectProperty ] | ^[ a owl:ObjectProperty ] ) * ?y .
> > }
> 
> The working group has not decided to incorporate this feature into the property paths specification in this round of SPARQL standardization. Some future working group may decide to introduce it, or may introduce variables in property paths.
> 
> >
> > Thanks for listening,
> > Doug.
> 
> We would be grateful if you would acknowledge that your comment has been answered by sending a reply to this mailing list.
> 
> Andy
> on behalf of the SPARQL working group
> 
Received on Tuesday, 2 November 2010 12:43:03 GMT

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