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[PropertyPath] Relation to PathLength

From: Seaborne, Andy <andy.seaborne@hp.com>
Date: Fri, 13 Mar 2009 21:27:07 +0000
To: Lee Feigenbaum <lee@thefigtrees.net>, Alexandre Passant <alexandre.passant@deri.org>
CC: SPARQL Working Group <public-rdf-dawg@w3.org>
Message-ID: <B6CF1054FDC8B845BF93A6645D19BEA3628D133820@GVW1118EXC.americas.hpqcorp.net>


> -----Original Message-----
> From: public-rdf-dawg-request@w3.org [mailto:public-rdf-dawg-request@w3.org]
> On Behalf Of Lee Feigenbaum
> Sent: 13 March 2009 19:36
> To: Alexandre Passant
> Cc: SPARQL Working Group
> Subject: Re: Next telecon features & beyond
> 
> Alexandre Passant wrote:
> >
> > Without any pathLength filtering, the query is simply a property path
> > query as proposed in [3], but that way of using a variable (rather than
> > including the regexp directly as in ":foo rdf:type/rdfs:subClassOf*
> > :bar") allows imho more extensibility, especially for that length feature.
> 
> Right, but [3] doesn't include variables in the path position. Putting
> my implementer's hat on, I think that allowing path variables is
> significantly more challenging to implement, so much so that I'd prefer
> to consider the two cases separately.
> 
> I'm happy to be convinced otherwise thogh :-)
> 
> Lee

Lee, Alex,

I can see overlap between Feature:PathLength and Feature:PropertyPaths but I read Feature:PathLength as introducing a new datatype, the path, with associated matching and expression operators.  Some of the aspects of each feature can be achieved with the other feature but not all.  PropertyPaths do not introduce a general path (it could be done that way - but it isn't necessary).

Introducing a new datatype into SPARQL (there was a suggestion about lists somewhere IIRC) is quite a significant step.  So for now, I'd prefer to keep them separate and let's explore the commonality and non-commonality through more examples. (I find concrete examples easier to work with on email than just general descriptions as examples test understanding better.)

	Andy

> 
> >
> > Cheers,
> >
> > Alex.
> >
> > [1]
> > http://www-sop.inria.fr/edelweiss/software/corese/v2_4_1/manual/next.php

> > [2] http://www.w3.org/2009/sparql/wiki/Feature:PathLength

> > [3] http://www.w3.org/2009/sparql/wiki/Feature:PropertyPaths

> >
> >> My understanding is that property paths allow me to specify in a
> >> regular expression-like way an explicit chain that connects two nodes.
> >> For path length, you need to start having variables match
> >> arbitrary-length paths between nodes, right? (Once you ahve a variable
> >> matching a path, then it's natural to add a function to get the length
> >> of that path.) And that seems like a whole other ball of wax to me.
> >>
> >> Am I misunderstanding?
> >>
> >> Lee
> >

Received on Friday, 13 March 2009 21:28:09 GMT

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