W3C home > Mailing lists > Public > public-rdf-dawg-comments@w3.org > July 2012

Re: Question about duplicate triples

From: David Booth <david@dbooth.org>
Date: Tue, 31 Jul 2012 16:26:13 -0400
To: Andy Seaborne <andy.seaborne@epimorphics.com>
Cc: public-rdf-dawg-comments@w3.org
Message-ID: <1343766373.2725.78123.camel@dbooth-laptop>
On Tue, 2012-07-31 at 17:10 +0100, Andy Seaborne wrote:
> 
> On 31/07/12 15:36, David Booth wrote:
> > 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?
> 
> Please see
> 
> http://lists.w3.org/Archives/Public/public-rdf-dawg-comments/2012Jul/0029.html

Thanks, that answers my question.

> 
> Please consider using the mailing list public-sparql-dev@w3.org for 
> general questions.  It allows for general discussion.

Oh!  I didn't realize that I could post to that list.  I had previously
tried to post to the RDF working group list, but found that only working
group members are permitted to post to it, so I assumed the same to be
true for the SPARQL working group.  Thanks for letting me know.

David


> 
> 	Andy
> 
> >
> >
> >
> 
> 

-- 
David Booth, Ph.D.
http://dbooth.org/

Opinions expressed herein are those of the author and do not necessarily
reflect those of his employer.
Received on Tuesday, 31 July 2012 20:26:41 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Tuesday, 31 July 2012 20:26:42 GMT