- From: Simon Gibbs <simon.gibbs@cantorva.com>
- Date: Tue, 02 May 2006 23:45:32 +0100
- To: public-rdf-dawg-comments@w3.org
- Message-ID: <4457E10C.5030606@cantorva.com>
Hello Following on from a chat on #swig I have a test case for discussion purposes. See attached file, or http://cantorva.com/2006NS/Section0214BlankNodesTestCase.rdf . I've implemented a SPARQL engine which implements blank nodes per section 2.8.3 which gives blank node labels query scope. Section 2.5.4 seems to contradict this giving labels a scope specific to the basic graph pattern. One contributor on #swig understood 2.5.4 to be the case. See notes in the attached RDF/XML file for the differences I estimate this will cause in the result sets. Essentially, given the attached data, ?category is bound to a value less frequently under the regime given by 2.8.3 since all patterns must match the same subject node rather than matching only on the variable ?mailbox. PREFIX ex: <http://example.org/exNS/> SELECT ?mailbox ?category WHERE { _:a ex:sender ?mailbox ; ex:recipient <mailto:alice@example.com> . OPTIONAL { _:a ex:sender ?mailbox; ex:category ?category . } } The wording in the spec that seems to be at the root of this confusion is: 2.5.4: "the scope of the blank node label being the basic graph pattern" 2.8.3: "Blank nodes have labels which are scoped to the query." both from http://www.w3.org/TR/rdf-sparql-query/ My questions are, is this a conflict or am I missing something? If so, what is that? Otherwise, can the WG please clarify the conflict? Finally, thanks to all for the all of great work going into SPARQL. Simon Gibbs Cantorva
Attachments
- text/rdf attachment: Section0214BlankNodesTestCase.rdf
Received on Wednesday, 3 May 2006 19:30:54 UTC