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

From: Michael Schneider <schneid@fzi.de>
Date: Tue, 8 May 2012 14:02:17 +0200
Message-ID: <4FA90B49.8010803@fzi.de>
To: Bijan Parsia <bparsia@cs.man.ac.uk>
CC: Ivan Herman <ivan@w3.org>, "Evain, Jean-Pierre" <evain@ebu.ch>, Ian Horrocks <ian.horrocks@cs.ox.ac.uk>, "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>
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

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Forschungszentrum Informatik (FZI) an der Universität Karlsruhe
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Vorstand: Dipl. Wi.-Ing. Michael Flor, Prof. Dr. Ralf Reussner,
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Received on Tuesday, 8 May 2012 12:02:49 UTC

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