- From: Antoine Zimmermann <antoine.zimmermann@emse.fr>
- Date: Wed, 19 Sep 2012 18:58:46 +0200
- To: Pat Hayes <phayes@ihmc.us>, "Peter F. Patel-Schneider" <pfpschneider@gmail.com>
- CC: RDF WG <public-rdf-wg@w3.org>
Pat and Peter, The so called minimal dataset semantics proposed in the wiki is not minimal, and this non-minimality causes the issues mentionned by Peter. The tricky entailment of http://www.w3.org/2011/rdf-wg/wiki/TF-Graphs/Minimal-dataset-semantics#Brain_twisters is an example of the trouble caused by the constraint that IRIs denoting the same resource must map to a single graph. It is not the proposal I initial wrote, and I support another proposal. My initial more-minimal proposal was: http://www.w3.org/2011/rdf-wg/wiki/index.php?title=TF-Graphs/Minimal-dataset-semantics&oldid=2438 Entailment is independent in the default graph and in the named graphs as long as the default graph is consistent. This addresses one of Peter's comment. Now, let us examine the situation wrt the consistency of the default graph. The argument comes from an implementation practice in SPARQL store. If we approve the Proposal made by Sandro, then such a practice is irrelevant to us for the definition of dataset semantics. When you want to exchange a dataset between systems, I doubt it would be a good idea to serialise the merge of all the graphs, in addition to serialising all the named graphs themselves. That would be insanely redundent. So, in the end, what gets exposed, and what has to be interoperable, does not (or should bot, if that's what people do) contain an unrestricted, unclean garbage of triples inside the default graph. I doubt that people are going to write TriG files where all the triples get duplicate because inside the implementation there was the "default as union" policy. Isn't this TriG file ridiculous? I wish it was inconsistent. { :s owl:differentFrom :s . # 10000 other triples from :g1 rdf:type owl:sameAs owl:sameAs . # 10000 other triples from :g2 } :g1 { :s owl:differentFrom :s . # 10000 other triples from :g1 } :g2 { :rdf:type owl:sameAs owl:sameAs . # 10000 other triples from :g2 } The more-minimal dataset semantics is not clashing with SPARQL. Before SPARQL 1.1 Entailment Regimes, there was no way to query an inconsistent graph with the default regime. With SPARQL 1.1, it is possible to sublit a query to an inconsistent graph, which may generate an error. But at any moment of the query resolution, only the semantics of graphs are used. The query engine has to resolve Basic Graph Pattern matching according to the graph-entailment regime, and build the complete answers to the query according to SPARQL algebra. Dataset-semantics is never involved. So, according to this view, I'm interested in knowing if there are still counter arguments from Pat or Peter. If there are, would the objection be a firm "-1" or something else? Best, -- Antoine Zimmermann ISCOD / LSTI - Institut Henri Fayol École Nationale Supérieure des Mines de Saint-Étienne 158 cours Fauriel 42023 Saint-Étienne Cedex 2 France Tél:+33(0)4 77 42 66 03 Fax:+33(0)4 77 42 66 66 http://zimmer.aprilfoolsreview.com/
Received on Wednesday, 19 September 2012 16:59:21 UTC