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Re: status of xsd:duration in RDF

From: Ivan Herman <ivan@w3.org>
Date: Mon, 21 May 2012 19:18:18 +0200
Cc: "Peter F. Patel-Schneider" <pfpschneider@gmail.com>, public-owl-wg@w3.org, Ian Horrocks <ian.horrocks@cs.ox.ac.uk>, "Public-Rif-Wg (E-mail)" <public-rif-wg@w3.org>, Boris Motik <boris.motik@cs.ox.ac.uk>
Message-Id: <8F95743C-E51C-471E-8D4B-03CB61AEB375@w3.org>
To: Michael Schneider <schneid@fzi.de>
Michael,

- The fundamental point is that duration will be added to the RDF D-interpretation the same way as the other datatypes, and the overall treatment of XSD datatypes will not change. Ie, there is no change on the current document except that duration will also be listed. At this moment, I cannot say whether gYear and the others will be added or not but if they are, they will be added the same way. 

- There is, actually, another change that will occur, per current agreement, namely that the XML Literal datatype will become optional. Maybe that is a point that may be taken into account when re-editing OWL: conformant RDF processors (so maybe the same for OWL?) are not _required_ to handle XML Literals. Also, the definition of the XML Literal's lexical and value space is to change (in my view, will be cleaner):

http://www.w3.org/2011/rdf-wg/meeting/2012-05-09#resolution_1

- Finally, we will probably (no formal resolution yet) add an HTML Literal, pretty much along the lines of an XML Literal, also meaning it to be optional.

Pat also said, on one of his mails[1], related to the XML Literal:

[[[
We could help with this by saying that semantic extensions MAY choose to treat XMLLIteral as a built-in datatype. That lets them off the hook editorially. But we should check with them.
]]]

Cheers

Ivan

[1] http://www.w3.org/mid/BE1404F2-3A60-4C74-8DEB-64439359B821@ihmc.us


On May 9, 2012, at 20:49 , Michael Schneider wrote:

> Hi Peter!
> 
> Am 09.05.2012 17:09, schrieb Peter F. Patel-Schneider:
> > Regardless of whether xsd:duration can make it into OWL 2, there is a
> > question of whether anyone in this group knows of any reason why
> > xsd:duration should not be added to RDF by the current RDF WG, aside
> > from a desire to have the datatypes in OWL match those in RDF.
> >
> > Any comments?
> 
> Two questions (with some implicit answers to your question):
> 
> 1) What other datatypes are under consideration by the RDF WG to be "added to RDF"? There are a lot of datatypes being mentioned in the original RDF standard, which were not taken into account by the OWL 2 and RIF specs, such as xsd:gYear, xsd:gMonthDay, xsd:gDay, xsd:gMonth. So, one could argue, if these datatypes are going to be added to RDF (again), why should we (the OWL WG) then care about xsd:duration? It'll be then just yet another datatype that is in RDF but not in OWL 2 and RIF.
> 
> 2) What does "adding to RDF" precisely mean? Mentioning the datatype somewhere in the spec by its name? Or making it a normative part of the RDF semantics? In RDF 1, the definitions of RDF-, RDFS- and D-interpretations only contained rdf:XMLLiteral as a normative part. There was one specific datatype map being mentioned in the chapter on D-entailment, called the "XSD datatype map" (the one with the non-OWL2 datatypes mentioned above), but it was not an official part of the semantics of any D-interpretation (as many people seem to believe), but was just a well-known datatype map, an example for how a "D" could look like (perhaps a "primus-inter-pares D", but not more). If "adding to RDF" is meant that way, then I would *not* care much, whether xsd:duration is included in the new version of the XSD datatype map or not. If, however, it is meant to become (together with its friends from the XSD datatype map) a normative part of any D-interpretation (which would be a big step from RDF 1), then I would care *much*, because any OWL 2 RDF-Based interpretation is a D-interpretation, and if all D-interpretations would include all the XSD datatypes from the RDF spec (plus, maybe, xsd:duration), this would mean that future OWL-N Full reasoners would have to support them all, which is quite a bit more than what OWL 2 Full reasoners are expected today (with possible implementation trouble here and there)! (To be mentioned: Most probably, this would then only be an issue for OWL N Full, not OWL N DL, as for current OWL 2 DL, the semantics and, in particular, the set of to-be-supported datatypes is specified independently from the RDF semantics specification).
> 
> So far from my slightly RDF-Based/OWL Full-centric point of view.
> 
> Best,
> Michael
> 
> -- 
> .........................................................
> Dipl.-Inform. Michael Schneider
> Research Scientist, IPE / WIM
> 
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----
Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
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FOAF: http://www.ivan-herman.net/foaf.rdf
Received on Monday, 21 May 2012 17:15:46 UTC

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