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Re: evaluating SPARQL w.r.t an RDF query language survey

From: Dan Connolly <connolly@w3.org>
Date: Thu, 07 Apr 2005 08:49:49 -0500
To: Jeen Broekstra <jeen@aduna.biz>
Cc: RDF Data Access Working Group <public-rdf-dawg@w3.org>
Message-Id: <1112881789.15073.803.camel@localhost>

On Thu, 2005-04-07 at 12:46 +0200, Jeen Broekstra wrote:
> On Apr 6, 2005, at 12:07 AM, Dan Connolly wrote:
> > A comment asks...
> > "How many of the 14 test questions in [1] does the current SPARQL spec
> > cover ?"
> >  --
> > http://lists.w3.org/Archives/Public/public-rdf-dawg-comments/2005Apr/0005.html
> >  -> http://www.aifb.uni-karlsruhe.de/WBS/pha/rdf-query/
> > 
> > I'm interested to take a crack at it, but I'd like some confirmation
> > from other WG members that I've got this right before I reply.
> > Perhaps it's worth making these into test cases...
> I am one of the co-authors of that report, so if I can help out in any 
> way let me know.

I think it would be great for you to add these cases to our test

If you're interested, send an ssh2 public key to EricP and me
and we'll try to arrange CVS write access. I presume you can
get in touch with Steve to learn anything you don't yet know
about how our test suite works.

> [snip]
> > 5 Quantification
> > Return the persons who are authors of all publications.
> > 
> > nope.
> > 
> > The langauges with "yes" in this column seem to
> > support closed-world assumptions that
> > we don't support in SPARQL.
> I'm guessing that you are referring to the FORALL operation used in 
> the example RQL query? Or more generally, to the notion of "all 
> publications" in the specification of the query?

Well, yes. The query says "all publications" but the "yes"
answers only regard "all publications mentioned in the file".

> Is universal quantification by definition something that falls outside 

No; I'm not aware of anything in our charter that makes it
necessarily out of scope; it's just that we haven't had
use cases, requirements, objectives, or design proposals
in that direction.

>  or can it be scoped (for example, employing quantification 
> on a named graph to allow closed-world assumption on that particular 
> graph)?

I'm not sure.
Maybe there's some way to do the "all publications mentioned
in this file" query with bound() and OPTIONAL too. I don't
have a good feel for the expressive capability of those two yet.

> > 6 Aggregation
> > Count the number of authors of a publication.
> > 
> > nope.
> > 
> > unique names assumption.
> I have trouble with this. I think that defining a counting operation 
> that does not count entities, but simply labels (URIs, bNodes, 
> literals), would be useful. This does not make any unique names 
> assumption, AFAICS. Counting would simply be a way of retrieving the 
> number of results a query would give, without giving the actual result.

Well, perhaps, but that's not how I understood the test query.
It says "count the number of authors," not "count the number of
terms used in the given data to refer to authors".

> Jeen
Dan Connolly, W3C http://www.w3.org/People/Connolly/
D3C2 887B 0F92 6005 C541  0875 0F91 96DE 6E52 C29E
Received on Thursday, 7 April 2005 13:49:51 UTC

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