- From: Andy Seaborne <andy.seaborne@epimorphics.com>
- Date: Mon, 21 Mar 2011 10:50:18 +0000
- To: Birte Glimm <birte.glimm@comlab.ox.ac.uk>
- CC: SPARQL Working Group <public-rdf-dawg@w3.org>
On 15/03/11 00:34, Birte Glimm wrote: > 18.6 > The overall SPARQL design can be used for queries which assume a more > elaborate form of entailment than simple entailment, by re-writing the > matching conditions for basic graph patterns. > > This is no longer true due to PPEs. I am not happy about this at all > and I assumed that PPEs are optional features. If they are not, it is > quite unfortunate that the so far existing extension point no longer > really is one and something has to be done at least to clarify this! Property paths are handled by maximising the rewrites to other SPARQL forms, including BGPs, and introducing new SPARQL algebra operators only where necessary. Therefore, evaluation of property paths does reduce to algebra+BGPs, just like any SPARQL query pattern. Would it be useful for the entailment document to discuss the issue that the property path syntax is compiled to SPARQL algebra forms. It would be useful to discuss the relationship of applications-defined relationships (which is what property paths do - give the application writer a chance to express complex relationships such as transitivity) and the ontology-defined relationships that manifest via entailment. This might include limitations on the patterns in the syntax although that weakens the expressivity otherwise given to the application query writer. Andy
Received on Monday, 21 March 2011 10:50:54 UTC