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Summary of recent issues on current query spec (to be discussed in detail after current WD round)

From: Axel Polleres <axel.polleres@deri.org>
Date: Sat, 9 Jan 2010 02:08:13 +0000
Message-Id: <198E1073-2E05-4362-84A8-7FF03CF738D6@deri.org>
To: SPARQL Working Group <public-rdf-dawg@w3.org>
This is a summary of some of the issues/errata to definitions in the current query spec 
that we stumbled over in some of the  discussions on entailment. 

While I don't think it makes sense to strive to resolve any of these for the next WDs,
I'd keep them ready for discussion in one of the coming TCs after publication
(Please let me know if I forgot anything or there are any other improvements/errata):

1) consistency requirement for entailment regimes

 Issue text: For efficient implementations, it might be undesirable to enforce 
 consistency checking, e.g. for RDFS. So, in order to follow:
 "The effect of a query on an inconsistent graph is not covered by this specification, 
  but must be specified by the particular SPARQL extension."
 My (Axel- chairthatoff) interpretation is that I don't see that this implies that an 
 extension has to uniquely define the behavior on 
 inconsistent graphs, actually it could leave several options open (e.g. for implementations that 
 do or don't perform consistency checking.)

2) uniqueness of scoping graph

 The current spec of extending BGP matching requires uniqueness of the scoping graph, whereas actually the definition
 of a scoping graph for simple entailment is only unique up to homomorphic (i.e. simple) equivalence:
  
 "1 -- The scoping graph, SG, corresponding to any consistent active graph AG is uniquely specified and is E-equivalent to AG."

 It is there fore discussed to clarify this condition, e.g.: 

 "The scoping graph, SG, corresponding to any consistent active graph
 AG is uniquely (modulo simple equivalence) specified and is E-equivalent to AG."
  
3) Definition of RDF-B

 ""The term RDF-L denotes the set of all RDF Literals, RDF-B the set of all blank nodes in RDF graphs"

Hmmm, why "in RDF graphs" and in *which* graphs? It might be clearer/easier to simply drop "in RDF graphs", 
or to specify which graphs are talked about here.

4) Definition of Pattern Instance Mapping

 Birte's suggested clarafication, cf. http://lists.w3.org/Archives/Public/public-rdf-dawg/2010JanMar/0029.html
Received on Saturday, 9 January 2010 02:08:47 GMT

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