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Re: [TF-PP] Zero-length paths (ACTION-251)

From: Birte Glimm <birte.glimm@comlab.ox.ac.uk>
Date: Wed, 9 Jun 2010 00:23:53 +0200
Message-ID: <AANLkTim_G6reP-xsiAS0szGzMU0Z6JkgKIGNubV5lgQU@mail.gmail.com>
To: Gregory Williams <greg@evilfunhouse.com>
Cc: SPARQL Working Group WG <public-rdf-dawg@w3.org>
Hm, yes. The problem is that these URIs do not have any meaning in
simple interpretations. Under RDFS semantics, you could argue that
rdfs:subPropertyOf is a relation over all properties, so anything that
is of type rdf:Property should be contained in the relations (if :p is
a property, then (:p, :p) is in the reflexive relation), but that
doesn't help standard SPARQL...
Birte

On 8 June 2010 17:51, Gregory Williams <greg@evilfunhouse.com> wrote:
> On Jun 8, 2010, at 11:45 AM, Birte Glimm wrote:
>
>> Thus, a (mathematically) natural interpretation would be to return
>> only subjects and objects because they are the elements of the
>> relations (as also Andy suggested below).  It still does what Greg
>> wants I believe. E.g. lets say G contains:
>> ex:a ex:mylabel "l1".
>> ex:mylabel rdfs:subPropertyOf rdfs:label
>>
>> Greg's query is:
>> SELECT ?label WHERE {
>>       ?p rdfs:subPropertyOf* rdfs:label .
>>       ?s ?p ?label .
>> }
>
> My issue with this example was specifically so that it would handle not only the case you show (with a subproperty of rdfs:label), but also ones where there is no schema information at all. If the data only contained:
>
> <s> rdfs:label "foo" .
>
> then I believe your approach wouldn't return any bindings for ?label, even though { ?label = "foo" } would be the intuitive result of the query, as far as I'm concerned.
>
> .greg
>
>



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Received on Tuesday, 8 June 2010 22:32:15 GMT

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