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Re: Datatypes

From: Bijan Parsia <bparsia@cs.man.ac.uk>
Date: Wed, 22 Aug 2007 11:37:34 +0100
Message-Id: <3DEB4FD7-480D-4ECB-9051-BBB7A1060613@cs.man.ac.uk>
Cc: Reto Bachmann-Gmür <reto@gmuer.ch>, semantic-web@w3.org
To: Dave Reynolds <der@hplb.hpl.hp.com>

On 22 Aug 2007, at 11:23, Dave Reynolds wrote:

> Bijan Parsia wrote:
>> On 21 Aug 2007, at 16:42, Reto Bachmann-Gmür wrote:
>
> (Hi Reto)
[snip]
>>> My question:
>>> - Anyone knows a place where such datatypes are already defined?
>> Not me.
>>> - Datatypes are typically defined in an XML-schema, is there an  
>>> ontology
>>> to do so in RDF?
>> RDF has pretty limited datatype support in general (both in the  
>> spec and in the tools...as far as I know).
>
> I thought most RDF tools supported a good range of XSD types.

I don't have a list, hence the caveat. What's a better  
statement....Well, it seems clear that any conforming RDF parser  
should respect arbitrary datatypes in assertions, at least in the  
sense of providing access to the datatype URI and the lexical form.   
I believe that most if not all of them do that. An RDF application  
(including a store) could choose to normalize the lexical form if it  
respected the value. I don't know what most systems do there. What  
I'm skeptical about is whether there is general support for D- 
Entailment (I'd expect at least a warning by a reasoner if a  
particular datatype were unknown to it).

> Jena also supports user defined types - both user defined XSD types  
> and generic user defined types. A type URI which is not recognized  
> will by default pass through safely (you can parse it, serialize  
> it, get it's lexical form etc) so the minimum you need to do is to  
> invent a URI for your datatype.

Yes, there's an ambiguity in "supports". Sorry 'bout that. I was  
thinking primarily about "supports the value space and entailments  
wrt it". Seems like Jena does some of that too.

> Reto, in your case it seems like all your types are variants on  
> strings where you might want to impose syntax constraints, in which  
> case defining regex restrictions on xsd:string seems like the easy  
> approach.

Agreed.

>> OWL has somewhat better support including required support for  
>> xsd:string and xsd:integer, plus at least defined support for  
>> other simple types:
>>     <http://www.w3.org/TR/2003/WD-owl-semantics-20030203/ 
>> syntax.html#2>
>> Deriving URIs for user defined datatypes was left unspecified in  
>> deference to the XML Schema working group. There's a discussion  
>> you might find interesting:
>>     <http://www.w3.org/TR/swbp-xsch-datatypes/>
>> (Pellet implemented the daml solution.)
>
> As does Jena.

Sorry, do you mean that Jena implements the daml solution? That's  
nice. We should have a list somewhere (heck, for all I know, pellet's  
support is derived in part from Jena!).

Does Jena also support the OWL 1.1 RDF vocabulary for defining  
datatypes? (Not that I'm convinced that this is, in general, a good  
idea).

Cheers,
Bijan.
Received on Wednesday, 22 August 2007 10:36:29 GMT

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