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Re: draft for my action item

From: Seaborne, Andy <andy.seaborne@hp.com>
Date: Mon, 04 Dec 2006 13:50:25 +0000
Message-ID: <457427A1.2000604@hp.com>
To: Pat Hayes <phayes@ihmc.us>
CC: RDF Data Access Working Group <public-rdf-dawg@w3.org>



Pat Hayes wrote:
> First very rough draft visible at
> 
> http://www.ihmc.us/users/phayes/SPARQL-BGP-semantics.html
> 
> I havnt yet tried to fit this elegantly into your algebra document, 
> Im afraid, or linked it to the test cases.
> 
> The missing proof at the end is elementary but tedious to write out, 
> maybe should be in an appendix somewhere. In fact, I'd be happy to 
> put the whole of the first section into an appendix, if we can make 
> an appendix be normative.
> 
> Feedback welcome.
> 
> Pat
> 

Pat,

Para 2 defines various possibilities for GQ for SPARQL.  I think we need to be 
more definite and specify one.  The skolemized version is a bit unusual so I 
see the decision as how accepting of told bnodes we are.  I'd guess 
implementations make G = GQ

What about defining it so that Q does not share any bnodes with G, putting the 
burden on Q, not GQ?  As we have to talk about SPARQL query strings so we can 
impose the condition that parsing does not generate a bnode shared with G.


Cardinality for SPARQL: the definition is for a binding of query variables 
then there is the answer set.  There is no conditions on the cardinality 
unless we take it to be implicitly one, which was contrary to the decision 
last week.

Oneway woudl be to map the bnodes in the Q as well, then restricting the 
mapping just to named variables, it seems cleaner to have a mapping, for 
SPARQL for simple entailement, from bnodes in the query to terms of G/GQ, then 
a separate mapping of the named variables.  Then the binding is the second 
mapping.

	Andy
Received on Monday, 4 December 2006 13:50:57 GMT

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