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Re: Datatype was RE: Confusion about Collections

From: Frank Manola <fmanola@mitre.org>
Date: Tue, 26 Nov 2002 08:23:36 -0500
Message-ID: <3DE375D8.7000504@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>

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





-- 
Frank Manola                   The MITRE Corporation
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Received on Tuesday, 26 November 2002 08:06:37 GMT

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