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Re: tests and inference? (and UNSAID)

From: Dan Connolly <connolly@w3.org>
Date: Sun, 19 Dec 2004 09:01:05 -0600
To: Steve Harris <S.W.Harris@ecs.soton.ac.uk>
Cc: RDF Data Access Working Group <public-rdf-dawg@w3.org>
Message-Id: <1103468465.3082.447.camel@dirk>

On Thu, 2004-12-16 at 15:17 +0000, Steve Harris wrote:
> On Thu, Dec 16, 2004 at 10:09:19 -0500, Kendall Clark wrote:
> > My point about the Sparql spec is that it doesn't help a person who
> > wants to figure out why all of her tests are failing because her
> > triple store defaultedly does RDFS inference (say) on all graphs. In
> > fact, if there's nothing in the test suite about this issue, and a
> > person goes and looks at the Sparql spec, the language about
> > orthogonality of inference and query misleads *further*.
> Thats true, but none of the test results we have approved so far alter if
> you have RDFS inference on. I hoped that was deliberate.

Well, no, I don't think so. In particular, it seems we had better
discuss the following two tests:

1. input graph:

:C1 rdfs:subClassOf :C2.
:x rdf:type :C1.


SELECT ?C WHERE (:x rdf:type ?C).

answer per current* editors draft:

?C binds to :C1
(no other results)

2. same input graph


SELECT ?x WHERE UNSAID (?x rdf:type :C2).

answer per current* editors' draft:

?X binds to :x.

* http://www.w3.org/2001/sw/DataAccess/rq23/ $Revision: 1.158 $
assuming I'm not making syntax errors, which I haven't checked

> My engine has no way to turn off inference (though it wouldn't be hard to
> add globaly), but I'd like it if that was possible on a per-statement way
> via the query language.

I'm not sure what you mean; it makes more sense, to me, to specify what
you're querying against in the FROM clause. If we wanted explicit
support for "turning RDFS inferencing off" in SPARQL, I'd expect it
to look something like:

	SELECT ?C FROM rdfs(<mydata.rdf>) WHERE ( :x rdf:type ?C).
	SELECT ?C FROM <mydata.rdf> WHERE ( :x rdf:type ?C).

As I discussed earlier...
RE: Test cases: source of a triple

... in N3, it's a matter of using these terms in the right places:


i.e. the graph contained in mydata.rdf vs


i.e. the graph you get by conjoining mydata with rdfs-rules and
computing the deductive closure.

> - Steve
Dan Connolly, W3C http://www.w3.org/People/Connolly/
D3C2 887B 0F92 6005 C541  0875 0F91 96DE 6E52 C29E
Received on Sunday, 19 December 2004 15:00:42 UTC

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