- From: Dan Connolly <connolly@w3.org>
- Date: Wed, 22 Dec 2004 09:09:38 -0600
- To: RDF Data Access Working Group <public-rdf-dawg@w3.org>
I think I have mentioned this in IRC now and then, but I don't think I have sent mail about it. Please specify the language without reference to implementations. That is, take out stuff like: "If a query processor encounters a function that it does not provide, the query is not executed and an error is returned." http://www.w3.org/2001/sw/DataAccess/rq23/#TestingExtensions $Revision: 1.160 $ of $Date: 2004/12/17 18:16:17 $ Stuff like "note that the query processor does not have to have any understanding of the values in the space of the datatype" is perhaps OK as informal explanation. "RDF systems are not required to implement the entailements expressed by these rules, but may choose to do so" looks like it refers to some standardized notion of "RDF system"; I'm not aware of one. Please ground it with a link if there is one. And what does "may choose to do so" mean? Does it impact definitions such as Query Results? If so, the language isn't well-defined; its definition depends on implementations. (hmm... where's the term that's like Query Results but factors in constraints, optionals, unsaid, and all that?) I prefer to get rid of the whole section 3.3 Implementation Requirements. If the WG really wants to get into software conformance clauses, (a) it will have a considerable impact on our schedule, which is already at risk; I'm not sure we can do that without extending the duration of the WG, which requires negotiating with various parties outside the WG, and (b) the language needs to be specified without reference to implementations anyway and (c) we'll need clear definitions for the product classes (some advice is available in section 2.2 What needs to conform of the QA spec guidelines http://www.w3.org/TR/2004/WD-qaframe-spec-20041122/#what-conform) This looks like a pretty clear problem: "The following are equivalent for a query processor that handles preciates for mathmatical expressions:" It seems to me that datatype entailments are no different from RDFS entailments; some systems pre-compute them and use the result as the input graph when evaluating queries. That doesn't change how queries work. The query written... WHERE ( ?x dc:title ?title ) ( ?x ns:price ?price ) ( ?price op:numeric-less-than 30 ) will only match if the input graph includes a triple ala <#x> op:numeric-less-than 30. I suggest rewriting "3.4 Constraints and Predicates" to be include discussion of RDFS, and making it clear that it's informative, i.e. not part of the definition of the query language. I was hoping we could leave the input graph that a service chooses fairly opaque for v1, but we don't seem to be able to avoid discussing service descriptions or complex FROM clauses or something. Hm... I think there's another issue brewing... -- Dan Connolly, W3C http://www.w3.org/People/Connolly/ D3C2 887B 0F92 6005 C541 0875 0F91 96DE 6E52 C29E
Received on Wednesday, 22 December 2004 15:09:05 UTC