- From: Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>
- Date: Tue, 2 Sep 2008 17:55:03 +0100
- To: Michael Schneider <schneid@fzi.de>
- Cc: "W3C OWL Working Group" <public-owl-wg@w3.org>
Thanks for the thoughtful review. Some responses in line below... On 2 Sep 2008, at 09:48, Michael Schneider wrote: > [related to ISSUE-130 and ISSUE-131 (Conformance and OWL RL > Unification)] > > Hi! > > I have read the Conformance proposal at > > <http://www.w3.org/2007/OWL/wiki/Conformance> > > It's a clearly written document. I have several comments/questions. > > * 1.1.1. > > """ > Any RDF/XML document is an OWL 2 Full ontology document. > """ > > I suggest to replace "RDF/XML document" by "RDF document" or "RDF > graph". > Whether something is a Full ontology should not depend on a > specific RDF > serialization. I agree. This was a hangover from OWL 1. I used RDF document, because conformance relates to concrete artefacts such as documents not abstract objects such as RDF graphs. > > * 1.1.1. > > """ > An OWL 2 Full ontology document is an OWL 2 RL > ontology document iff it can be successfully > parsed using the canonical RDF parsing process > and the resulting ontology in the functional-style > syntax satisfies all the restrictions on OWL 2 RL ontologies > """ > > Now I understand that one of the purposes of the (so far) OWL RL DL > syntax > is to define /syntactic/ conformance. For example, the following > RDF graph > (aka OWL 2 Full ontology) is /not/ a syntactically conformant OWL RL > ontology: > > ex:C rdfs:subClassOf _:x > _:x owl:unionOf (SEQ ex:D1 ex:D2) > > because, after the reverse mapping, it would not meet the RL syntax > restrictions. I'm personally fine with this. > > * 1.2.1. > > """ > An OWL 2 entailment checker takes as input > two OWL 2 ontology documents O1 and O2 > """ > > Isn't it better to talk about "two /imports-closed collections of/ > OWL 2 > ontology documents"? I did think about making the input to entailment checkers be something that would abstract away from imports related issues and perhaps even from parsing issues. I decided not to do this, because it would solve one problem by introducing another. Computing the imports closure is quite a complex process, and is dependent on several factors, including document locations. If we were going to do as you suggest here, then I think we would need to define something like an "OWL 2 imports-closure checker", and define comformance criteria for that. In the end, it seems simpler to bundle all of this into the definition of a single artefact. > > * 1.2.1. > > """ > and either the Model-Theoretic Semantics [OWL 2 Semantics] > or the RDF-Based Semantics [OWL 2 RDF-Based Semantics] > """ > > I just want to state that the RDF-Based Semantics is also a model- > theoretic > semantics, so this is not a useful distinction criterion. These are what the documents are currently called, so in that sense it is a very useful distinction. You may want to have a discussion about these names. > > * 1.2.1 > > """ > An OWL 2 entailment checker returns one word, > being True, False, or Unknown. > """ > > Perhaps, it's better to talk about "result" instead of "word". I agree. I changed the document accordingly. > > * 1.2.1 > > """ > An OWL 2 Full entailment checker is an OWL 2 entailment checker > that takes RDF/XML documents as input > """ > > Again "RDF/XML". But here, one can simply write "OWL 2 Full ontology > documents", because this term has already been defined elsewhere, > and it > would also be better in line with the rest of the "entailment checker" > definitions in this section. I refer to RDF here as it is more direct -- the definition of an OWL 2 Full ontology document is just that it is an RDF document. I wonder if we need to define OWL 2 Full ontology document at all? > > * 1.2.1 Analog for "OWL 2 RL entailment checker". But my question > is: Should > it be "OWL 2 /Full/ ontology documents" or "OWL 2 /RL/ ontology > documents"? It should be OWL Full ontology document / RDF document. > > * 1.2.1 > > """ > An OWL 2 RL entailment checker > [...] MUST return True only when O1 entails O2, > and it must return False > only when FO(O1) ? R does not entail FO(O2) > under the standard first-order semantics > """ > > Just to be clear: This means that there can be two conformant OWL 2 RL > entailment checkers C1 and C2, where for the same query "G_L |= > G_R ?" C1 > answers "False" (because G_R does not follow from G_L via the > rules), while > C2 answers "True" (because G_R follows from G_L via the Full > semantics). I > suggest that we state it explictly that this is intended. Otherwise > people > might get confused and think that this is a bug. This could be explicitly stated. We could also/instead strengthen the statement about warnings when the input ontologies are such that this could arise -- currently implementations MAY issue such a warning; this could be strengthened to SHOULD or MUST. > > * 1.2.1: "terminating and complete entailment checker" > > """ > reject the input as syntactically invalid > """ > > I don't understand what this means in the case of OWL RL. According to > 1.1.1, RDF seems to be the reference syntax, but RDF graphs are > only said to > be "RL conformant", if they can be successfully parsed into > Functional Style > syntax and satisfy the RL restrictions. So I wonder whether all RDF > graphs > or only those matching the RL restrictions (the "syntactically OWL RL > conformant ontology documents"!) are syntactically valid input to > an OWL RL > entailment checker. Perhaps it is meant that an OWL RL entailment > checker > MAY reject syntactically non-conformant OWL 2 RL documents, but if it > accepts them, then it has to provide the True/False/Unknown > behavior as > stated (e.g. it must not say "True", if the OWL Full semantics do not > entail). I would like to see some clarification here. This is a general statement covering all checkers. In the case of OWL RL checkers, it is clearly stated that they take RDF documents as input, so I don't see any confusion there. Input could be rejected as syntactically invalid if, e.g., it isn't and RDF graph. > > * 1.2.1: > > """ > An OWL 2 entailment checker is terminating if, > given sufficient memory resources > """ > > I think that two slight clarifications are needed here: > > (1) Is by "given sufficient memory resources" meant that the > amount of > memory is determined "a priorily" by the problem size? Or that > memory can be > appended on demand, such as in the case of a printer running out of > paper? I don't see the problem with this statement -- nothing needs to be said (or should be said) about procedural mechanisms for determining or allocating memory. > > (2) Definition of "completeness": Does this definition allow an > input on > which the entailment checking process does not terminate? Or is the > definition of termination already part of the definition of > completeness? No. Many algorithms used in theorem proving are sound and complete but non-terminating. Ian > > Best, > Michael > >> -----Original Message----- >> From: Ian Horrocks >> Sent: Monday, August 25, 2008 1:27 PM >> To: public-owl-wg Group WG >> Subject: ISSUE-130 / ACTION-194 Come up with a proposal for >> conformance >> >> >> A draft proposal is now available in the Wiki [1]. The idea is that >> this would become the conformance section in the Test document [2]. >> >> Ian >> >> [1] http://www.w3.org/2007/OWL/wiki/Conformance >> [2] http://www.w3.org/2007/OWL/wiki/Test#Conformance > > -- > Dipl.-Inform. Michael Schneider > FZI Forschungszentrum Informatik Karlsruhe > Abtl. Information Process Engineering (IPE) > Tel : +49-721-9654-726 > Fax : +49-721-9654-727 > Email: Michael.Schneider@fzi.de > Web : http://www.fzi.de/ipe/eng/mitarbeiter.php?id=555 > > 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 > Az: 14-0563.1 Regierungspräsidium Karlsruhe > Vorstand: Rüdiger Dillmann, Michael Flor, Jivka Ovtcharova, Rudi > Studer > Vorsitzender des Kuratoriums: Ministerialdirigent Günther Leßnerkraus >
Received on Tuesday, 2 September 2008 16:55:45 UTC