- From: Michael Schneider <schneid@fzi.de>
- Date: Tue, 26 Jul 2011 14:34:26 +0200
- To: <public-rdf-dawg-comments@w3.org>
Dear all! Document: SPARQL 1.1 Entailment Regimes State: LCWD The definition tables for the entailment regimes have an entry "Illegal Handling". It is generally defined that a system must signal an error, if either the queried graph or the query is not a syntactically valid RDF graph or BGP. In the case of the "OWL 2 Direct Semantics Entailment Regime" (Chap. 6), there is additional treatment for the special case that the graph or the query is not an OWL DL ontology: If the queried ontology is not an OWL 2 DL ontology or the query is not legal for the ontology, the system MAY refuse the query and raise a QueryRequestRefused error or the system MAY use only a subset of the triples in the ontology or query. In general, I would be very cautious about specifying required ("MUST") behavior of a system in the case of syntactically invalid input. This may be too much of a requirement for an implementer to provide a compliant system, and might significantly affect the performance of a system due to additional checks. So, I suggest to reconsider your decision of how to handle syntactically invalid input: maybe a "SHOULD" is sufficient, or maybe nothing at all should be said. The latter would have the advantage that future extensions, such as support for generalized RDF (e.g. bnodes in predicate position) or named graphs beyond what SPARQL allows today would be possible without breaking compliance to SPARQL 1.1. In any case, I strongly propose to /not/ make any concrete suggestions of the form: "on invalid OWL DL input, a system may only use a subset of the triples in the query". Not even with a "MAY". This makes a wrong behavior with unexpected results on wrong input into a kind of "best practice recommendation" to implementors and leads to certain expectations of users. If a system works outside its specification, there should be either a strong requirement to not process the input (as currently for illegal RDF data), or nothing at all should be said, so the system behavior is strictly implementation dependent. It is then up to the implementor to do what he considers best (and potentially to describe the behavior in the system's manual). Again, system implementers may decide to support more than plain OWL 2 DL (e.g. by relaxing on the global syntactic constraints to retain decidability), and there should not be a general expectation that the system will use only parts of the input query in such cases. Best regards, Michael -- Dipl.-Inform. Michael Schneider Research Scientist, Information Process Engineering (IPE) Tel : +49-721-9654-726 Fax : +49-721-9654-727 Email: michael.schneider@fzi.de WWW : http://www.fzi.de/michael.schneider ============================================================================== FZI Forschungszentrum Informatik an der Universität Karlsruhe Haid-und-Neu-Str. 10-14, D-76131 Karlsruhe Tel.: +49-721-9654-0, Fax: +49-721-9654-959 Stiftung des bürgerlichen Rechts Stiftung Az: 14-0563.1 Regierungspräsidium Karlsruhe Vorstand: Dipl. Wi.-Ing. Michael Flor, Prof. Dr. rer. nat. Ralf Reussner, Prof. Dr. rer. nat. Dr. h.c. Wolffried Stucky, Prof. Dr. rer. nat. Rudi Studer Vorsitzender des Kuratoriums: Ministerialdirigent Günther Leßnerkraus ==============================================================================
Received on Tuesday, 26 July 2011 12:35:06 UTC