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

From: Gregory Williams <greg@evilfunhouse.com>
Date: Tue, 8 Jun 2010 11:51:34 -0400
Cc: SPARQL Working Group WG <public-rdf-dawg@w3.org>
Message-Id: <4EF7BB0E-A86B-44DD-A521-C3CFCFDC0538@evilfunhouse.com>
To: Birte Glimm <birte.glimm@comlab.ox.ac.uk>
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.

Received on Tuesday, 8 June 2010 15:52:31 UTC

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