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Re: Question about duplicate triples

From: David Booth <david@dbooth.org>
Date: Tue, 31 Jul 2012 10:36:34 -0400
To: public-rdf-dawg-comments@w3.org
Message-ID: <1343745394.2725.72040.camel@dbooth-laptop>
On Mon, 2012-07-30 at 18:18 -0400, David Booth wrote:
> Suppose I LOAD a single file of NTriples into a named graph foo:, and
> that file contains some duplicate triples such as:
>   _:bnode <http://example/ppp> <http://example/vvv> .
>   _:bnode <http://example/ppp> <http://example/vvv> .
>   _:bnode <http://example/ppp> <http://example/vvv> .
> According to the RDF Semantics, an RDF graph is a *set* of triples.
> Hence, AFAIK the above file represents an RDF graph containing *one*
> triple, and the graph is lean.
> If I then query that named graph as follows, how many solutions should I
> get?
>   SELECT * WHERE { GRAPH foo: { ?s ?p ?v } }
> Is the SPARQL server permitted to return more than one solution (i.e.,
> duplicates) in this case?
> I am aware of the DISTINCT keyword, but I always understood it as being
> intended for situations where the query could generate multiple
> candidate solutions, which is not the situation in this case.  It seems
> a little weird if a SPARQL server might return multiple solutions in
> this case, but would it still be conforming to the SPARQL spec if it
> did? 

To further elaborate, if I issue this query in the above situation

  SELECT (COUNT(*) AS ?count) WHERE { GRAPH foo: { ?s ?p ?v } }

would any number greater than zero be a conforming result for ?count ?

Or in a more general sense, if DISTINCT is not used, are the only
semantically distinguishable values for COUNT: (a) zero; and (b) at
least one?

David Booth, Ph.D.

Opinions expressed herein are those of the author and do not necessarily
reflect those of his employer.
Received on Tuesday, 31 July 2012 14:37:03 UTC

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