- From: Dan Connolly <connolly@w3.org>
- Date: Tue, 29 Mar 2005 11:01:30 -0600
- To: public-rdf-dawg-comments@w3.org, Geoff Chappell <geoff@sover.net>
Geoff writes: [...] > I realize the whole question assumes an acceptance of the logical > interpretation of OPTIONAL. Whether or not the working group considers that > to be valid, I think this test case clearly illustrates the need for some > formal definition of the semantics of OPTIONAL (i.e. I don't think you can > use test cases alone to define the behavior). Both the current editor's draft and the latest public working draft give this formal specification: [[ Definition: Optional Matching Given graph pattern GP1, and graph pattern GP2, let GP = (GP1 union GP2). The optional match of GP2 of graph G, given GP1, defines a pattern solution PS such that: If GP matches G, then the solutions of GP is the patterns solutions of GP else the solutions are the pattern solutions of GP1 matching G. ]] -- http://www.w3.org/2001/sw/DataAccess/rq23/#OptionalMatchingDefn http://www.w3.org/TR/2005/WD-rdf-sparql-query-20050217/#OptionalMatchingDefn This design was confirmed by WG decision http://www.w3.org/2001/sw/DataAccess/ftf5-bos.html#item_03 after explicitly considering the design where "A optional B" is interpreted as "A & (B v True)" and finding that it returns unhelpful solutions. http://www.w3.org/2001/sw/DataAccess/ftf5-bos.html#item02 I'll continue to study the test case that you write about, but meanwhile, I just wanted to bring to your attention the current formal definition. -- Dan Connolly, W3C http://www.w3.org/People/Connolly/ D3C2 887B 0F92 6005 C541 0875 0F91 96DE 6E52 C29E
Received on Tuesday, 29 March 2005 17:01:31 UTC