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Fred Zemke draft: general framework

From: Jorge Pérez <jperez@ing.puc.cl>
Date: Thu, 22 Jun 2006 10:19:43 -0400 (CLT)
Message-ID: <64405.146.155.4.12.1150985983.squirrel@mail.ing.puc.cl>
To: public-rdf-dawg-comments@w3.org
Cc: jperez@ing.puc.cl

This is a list of mails between me and FredZ about his (now public) draft
on formalization of SPARQL semantics.

http://lists.w3.org/Archives/Public/public-rdf-dawg/2006AprJun/0170.html

specifically about simple entailment to obtain solutions.
- jorge

---------------------------- Mensaje original ----------------------------
Asunto: Re: draft
De:     Jorge  Pérez <jperez@ing.puc.cl>
Fecha:  Jue, 15 de Junio de 2006, 5:12 pm
Para:   "Fred Zemke" <fred.zemke@oracle.com>
--------------------------------------------------------------------------

I am reading your draft in detail and will give you comments soon...
I have just a little question about the definition of solutions

consider the dataset D:

(a, b, a)
(X, b, Y)

whit X and Y blank nodes (the rest URIs), how many solutions has the
triple pattern

?q b ?q

I think that the mappings ?q -> a, ?q -> X, and ?q -> Y are all solutions,
am I right? because D simply entails all the following graphs

(a, b, a)
(X, b, Y)

(a, b, a)
(X, b, Y)
(X, b, X)

(a, b, a)
(X, b, Y)
(Y, b, Y)

am I making a mistake? if this is correct, is there a problem in having 3
distincts solutions for this pattern?

- jorge

---------------------------- Mensaje original ----------------------------
Asunto: Re: draft
De:     "Fred Zemke" <fred.zemke@oracle.com>
Fecha:  Jue, 15 de Junio de 2006, 8:30 pm
Para:   jperez@ing.puc.cl
--------------------------------------------------------------------------

interesting example.  I personally hope the answer is that only ?q -> a is a
 solution, but I have not yet been able to work through all the definitions
 to decide this one way or the other.  I'll let you know when I figure
 something out.

 Fred

---------------------------- Mensaje original ----------------------------
Asunto: Re: draft
De:     Jorge  Pérez <jperez@ing.puc.cl>
Fecha:  Vie, 16 de Junio de 2006, 9:03 am
Para:   "Fred Zemke" <fred.zemke@oracle.com>
--------------------------------------------------------------------------

To avoid this sort of "problems" (surely there are more examples like the
one i showed you) in our paper we made the (strong) assumption that the
dataset is lean. I think it is a good starting point, this simplify a lot
the definitions in the case of simple entailment. Another more theoretical
form of defining a solution is that the solution must be the same *as if
the dataset were lean*, this avoid the (strong) assumption and pass the
problem to implementors... but, who cares about implementation anyway? ;-)

- jorge
Received on Thursday, 22 June 2006 15:22:11 GMT

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