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Re: Datatype was RE: Confusion about Collections

From: Patrick Stickler <patrick.stickler@nokia.com>
Date: Tue, 26 Nov 2002 15:24:12 +0200
Message-ID: <002f01c2954f$1c02dd60$4b9316ac@NOE.Nokia.com>
To: "ext Frank Manola" <fmanola@mitre.org>
Cc: "ext Shelley Powers" <shelleyp@burningbird.net>, <www-rdf-comments@w3.org>, "Brian McBride" <bwm@hplb.hpl.hp.com>



[Patrick Stickler, Nokia/Finland, (+358 40) 801 9690, patrick.stickler@nokia.com]


----- Original Message ----- 
From: "ext Frank Manola" <fmanola@mitre.org>
To: "Patrick Stickler" <patrick.stickler@nokia.com>
Cc: "ext Shelley Powers" <shelleyp@burningbird.net>; <www-rdf-comments@w3.org>; "Brian McBride" <bwm@hplb.hpl.hp.com>
Sent: 26 November, 2002 15:23
Subject: Re: Datatype was RE: Confusion about Collections


> 
> Patrick Stickler wrote:
> 
> > 
> > [Patrick Stickler, Nokia/Finland, (+358 40) 801 9690, patrick.stickler@nokia.com]
> > 
> > 
> > ----- Original Message ----- 
> > From: "ext Shelley Powers" <shelleyp@burningbird.net>
> > To: "Shelley Powers" <shelleyp@burningbird.net>; <fmanola@mitre.org>
> > Cc: <www-rdf-comments@w3.org>
> > Sent: 25 November, 2002 19:05
> > Subject: Datatype was RE: Confusion about Collections
> > 
> > 
> > 
> >>
> >>>Also, Frank, a question on dates: I've seen references to
> >>>multiple documents about what date types are supported. I imagine
> >>>that we can use RDFS to provide instructions to consumers of our
> >>>vocabulary as to which date format is being supported. Or do we
> >>>use rdf:datatype? There's quite a bit of discussion on data
> >>>types, but it seems disjointed. I can't help thinking that the
> >>>primer could bring this together.
> >>>
> >>>Also question: you all aren't really going to support values of
> >>>'"1999-08-16"^^xsd:date', are you? No offense, but this horrid.
> >>>No offense again, but this is absolutely horrid. What's wrong
> >>>with using RDFS to define the data type, rather than making the
> >>>value into an intelligent value (ie data type is incorporated
> >>>into the instance, rather than the vocabulary definition)?
> >>>Embedding intelligence into values is the worst thing you can do
> >>>for a data model, regardless of model meta-structure.
> >>>
> >>>This is a broader question to group, or a request clarification
> >>>if I'm reading this wrong. I'm hoping I'm reading this wrong.
> >>>
> >>>Shelley
> >>>
> >>>
> >>As a point of clarification on this, it isn't the format that bothers me --
> >>it's the tying the datatype to instances rather than vocabulary. I know that
> >>RDF/xml uses rdf:datatype rather than  '"1999-08-16"^^xsd:date', but this
> >>again attaches the datatype to the instance, rather than the vocabulary. So,
> >>I could use http://www.w3.org/2001/XMLSchema#date for a date column that has
> >>data of 199-10-10, and use http://www.w3.org/2001/XMLSchema#integer for
> >>another instance of the vocabulary (another document), and this means time
> >>in seconds from a set date. Both are accurate, but neither is compatible.
> >>
> >>See the problems?
> >>
> >>However, if we attach the rdf:datatype to the definition of the vocabulary
> >>itself rather than any specific document, then the creators of the
> >>vocabulary can say that this property takes integers representing number of
> >>seconds since whatever. And all instances (documents) based on the
> >>vocabulary would be compatible.
> >>
> >>Sorry, I know this is my strong data background talking, but I can see a
> >>nightmare in the making with this one.
> >>
> >>Shelley
> >>
> > 
> > Shelley,
> > 
> > You can specify the datatype range of a property using rdfs:range to
> > accomplish this. E.g.
> > 
> >    my:dateProperty rdfs:range xsd:date .
> > 
> > And this asserts that all values of my:dateProperty are expected
> > to be of type xsd:date.
> > 
> > Cheers,
> > 
> > Patrick
> > 
> 
> 
> Keeping in mind, however, that the actual *instances* of the datatype 
> values must still explicitly cite the datatype (if I remember this 
> correctly).  That is, saying
> 
> my:dateProperty rdfs:range xsd:date .
> 
> in the schema doesn't mean that you can write triples like
> 
> 
> ex:myPurchaseOrder my:dateProperty "1999-08-16"
> 
> and expect "1999-08-16" to be interpreted as an xsd:date.
> 
> Instead, the triples have to be written like
> 
> ex:myPurchaseOrder my:dateProperty "1999-08-16"^^xsd:date
> 
> Right, Patrick?
> 
> --Frank

Right, the datatype must be specified explicitly for every single
occurrence of every datatype value (unfortunately ;-)

Patrick
Received on Tuesday, 26 November 2002 08:40:11 GMT

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