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Re: status of xsd:duration in OWL (and RIF and SPARQL) - ACTION-164: RDF WG

From: Ian Horrocks <ian.horrocks@cs.ox.ac.uk>
Date: Tue, 8 May 2012 22:39:21 +0100
Cc: Bijan Parsia <bparsia@cs.man.ac.uk>, Ivan Herman <ivan@w3.org>, "Evain, Jean-Pierre" <evain@ebu.ch>, "public-owl-wg@w3.org" <public-owl-wg@w3.org>, "Public-Rif-Wg (E-mail)" <public-rif-wg@w3.org>, "Peter F. Patel-Schneider" <pfpschneider@gmail.com>, Sandro Hawke <sandro@w3.org>
Message-Id: <732C5A58-4B3B-4886-9789-F17F35696664@cs.ox.ac.uk>
To: Michael Schneider <schneid@fzi.de>
Not answering specifically to Michael's point, but simply continuing this thread...

The discussion to date simply confirms me in my belief that significant technical due diligence would be required before adding these datatypes, and thus that it would not be appropriate to undertake such an addition without fully reconstituting the WG and giving everyone the chance to review the proposal -- and presumably even giving the membership as a whole the opportunity to review the proposed change via the usual LC, CR, and PR mechanism. This would go far beyond what was agreed when the WG went into suspended animation, and I think it is clear that it simply can't happen as part of the OWL WG activity. 


the technical complexity is such that 

On 8 May 2012, at 13:02, Michael Schneider wrote:

> Am 08.05.2012 10:38, schrieb Bijan Parsia:
>> On 8 May 2012, at 07:49, Ivan Herman wrote:
>> [snip]
>>> Jean-Pierre,
>>> without taking side on whether duration should or should not be part of OWL 2 for reasoning (I do not have enough technical baggage to comment on that): if you use duration today, it is valid RDF (even if RDF2004 still refers to duration as a SHOULD NOT be used, but that might change now with XSD1.1). Not being part of OWL 2 means that you do not get OWL 2 datatype reasoning on those literal values; I presume an OWL 2 reasoner would treat those literal values pretty much as strings.
>> Nope, it would (if conforming) reject them and the surrounding ontology. Actual reasoners differ in how they handle unknown datatypes in "aggressive repair" mode.
> My understanding is that an OWL 2 DL-compliant reasoner does not need to reject an ontology that uses datatypes beyond the official set of OWL 2 datatypes.
> The reason is that the behaviour of OWL 2 DL reasoners is only specified for valid OWL 2 DL ontology documents (see the definition of tool conformance for OWL 2 DL entailment checkers at [1]). An OWL 2 ontology document that uses non-OWL 2 datatypes, in particular those from the reserved XSD namespace, such as "xsd:time", would not be a valid OWL 2 DL ontology according to the definition of OWL 2 DL document conformance in [2], in conjunction with the definition of OWL 2 DL ontologies in Sec. 3 of the OWL 2 Structural Specification [3], which is detailed in Sec. 5.2 on "Datatypes" [4]:
> """
> The conditions from the previous paragraph and the restrictions on datatypes in Section 11.2 require each datatype in an OWL 2 DL ontology to be rdfs:Literal, one of the datatypes from Section 4, or a datatype defined by means of a datatype definition (see Section 9.4).
> """
> Here, the "datatypes from Section 4" are the official OWL 2 datatypes.
> Hence, an OWL 2 DL reasoner may do whatever it wants with such an "extended" OWL ontology, in particular, it may but does not need to reject it, but may interpret such an ontology in whatever way it likes... even in a meaningful way. :-)
> Michael
> [1] <http://www.w3.org/TR/2009/REC-owl2-conformance-20091027/#Entailment_Checker>
> [2] <http://www.w3.org/TR/2009/REC-owl2-conformance-20091027/#Syntactic_Conformance>
> [3] <http://www.w3.org/TR/2009/REC-owl2-syntax-20091027/#def_ontology>
> [4] <http://www.w3.org/TR/2009/REC-owl2-syntax-20091027/#Datatypes>
> -- 
> .........................................................
> Dipl.-Inform. Michael Schneider
> Research Scientist, IPE / WIM
> FZI Forschungszentrum Informatik
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> 76131 Karlsruhe, Germany
> Tel.: +49 721 9654-726
> Fax: +49 721 9654-727
> michael.schneider@fzi.de
> www.fzi.de
> .........................................................
> Forschungszentrum Informatik (FZI) an der Universität Karlsruhe
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Received on Tuesday, 8 May 2012 21:39:53 UTC

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