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Re: [Entailment] D-entailment (and upwards) issue?

From: Birte Glimm <birte.glimm@comlab.ox.ac.uk>
Date: Tue, 11 May 2010 09:27:03 -0400
Message-ID: <AANLkTim_G6n43YOVCrhErw42ni342K8QecbZPgGUryZ-@mail.gmail.com>
To: Axel Polleres <axel.polleres@deri.org>
Cc: SPARQL Working Group <public-rdf-dawg@w3.org>
On 11 May 2010 02:53, Axel Polleres <axel.polleres@deri.org> wrote:
[snip]
> G:  :s :p "1"^^xs:integer
> Query1: SELECT * WHERE {?S ?P "1.00"^^xs:decimal }
> Query2: SELECT * WHERE {?S ?P ?O FILTER(?O = "1.00"^^xs:decimal) }

I had a small panic attack too, but thanks to Andy's reply I am over
that and I think we are fine.

As I pointed out in the entailment doc, some queries only yield the
expected results when canonicalisation is applied, but whether or not
that is done when loading the graph from a serialisation document is
up to the implementation. In the above example canonicalisation has no
effect and you will get the expected answers in any case. The only
time canonicalisation matters is when variables are bound to data
values. At the moment, C2 restricts bindings to terms from the
relevant vocabulary for the regime or values that occur in the graph,
which might be canonicalised or not. If we want to force
canonicalisation, we could either specify parsing in more detail or I
could tweak condition C2 and restrict bindings to
- terms from the vocabulary dV-Minus or
- *IRIs* in the Skolemized graph or
- canonicalised versions d_c of data values d occurring in the queried
graph G.

As Andy argued at F2F3 the parsing process is deliberately
underspecified regarding this, so we might not want to start changing
that. I am not sure how much support a tweaked C2 condition would get,
which does only effect systems that want to implement a data aware
entailment regime. Maybe that's something to have a straw poll about?

[snip]
> p.s.: think I also found a small typo in the section 4.1 ....
>
> "If the parsing process involves canonicalization, then the obtained graph will contain just two nodes (one for ex:s and one for the
>            data value 100.0) connected by one edge (for ex:s)"
>
> should be:
>
> "If the parsing process involves canonicalization, then the obtained graph will contain just two nodes (one for ex:s and one for the
>            data value 100.0) connected by one edge (ex:p)"
>

fixed.

>
>



-- 
Dr. Birte Glimm, Room 306
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Received on Tuesday, 11 May 2010 13:27:36 GMT

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