- From: <jos.deroo@agfa.com>
- Date: Sat, 7 Jan 2006 17:42:34 +0100
- To: tessaris@inf.unibz.it
- Cc: Dan Connolly <connolly@w3.org>, Enrico Franconi <franconi@inf.unibz.it>, Pat Hayes <phayes@ihmc.us>, RDF Data Access Working Group <public-rdf-dawg@w3.org>, public-rdf-dawg-request@w3.org
Sergio Tessaris wrote:
> By checking the entailment in the naive way, the bnode names are
> scoped to a single solution pattern, and not across an answer set.
>
> Consider the following dataset:
> _:a :r _:a
> _:a :p _:b
> _:b :url <http://example.org>
>
> and the query:
> SELECT * { ?x ?p ?y }
>
> Under the G |= S(P) semantics, the server is allowed to return an
> answer set like:
>
> ?x ?p ?y
> ----------------
> _:b12 :r _:b13
? _:b26 :p _:b27
> _:b40 :url <http://example.org>
Fine, I can see and test that
_:a :r _:a.
_:a :p _:b.
_:b :url <http://example.org>.
simply entails
_:b12 :r _:b13.
_:b26 :p _:b27.
_:b40 :url <http://example.org>.
> but even the unsettling
>
> ?x ?p ?y
> ----------------
> _:b12 :r _:b13
> _:b26 :p _:b13
> _:b12 :url <http://example.org>
but how could it ever entail
_:b12 :r _:b13.
_:b26 :p _:b13.
_:b12 :url <http://example.org>.
My proposed test case would be
Data
_:a :r _:a.
_:a :p _:b.
_:b :url <http://example.org>.
Query
SELECT * { ?x ?p ?y }
Answer
?x ?p ?y
-------------------------------
_:a_0 :r _:a_0
_:a_0 :p _:b_0
_:b_0 :url <http://example.org>
and also that
?x ?p ?y
-------------------------------
_:a_0 :r _:a_0
_:a_0 :r _:a_1
_:a_0 :p _:b_0
_:b_0 :url <http://example.org>
is a good answer
but
?x ?p ?y
-------------------------------
_:a_0 :r _:a_1
_:a_0 :p _:b_0
_:b_0 :url <http://example.org>
isn't a good answer.
So that are actually 3 test cases.
--
Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/
Received on Saturday, 7 January 2006 16:42:50 UTC