W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > November 2001

RE: ACTION 2001-11-02#02: Datatyping use-cases from CC/PP

From: Pat Hayes <phayes@ai.uwf.edu>
Date: Wed, 7 Nov 2001 14:53:34 -0600
Message-Id: <p0510105fb80f4dfe2c6c@[65.212.118.166]>
To: Patrick.Stickler@nokia.com
Cc: w3c-rdfcore-wg@w3.org
>  > -----Original Message-----
>>  From: ext Pat Hayes [mailto:phayes@ai.uwf.edu]
>>  Sent: 06 November, 2001 20:17
>>  To: Stickler Patrick (NRC/Tampere)
>>  Cc: w3c-rdfcore-wg@w3.org
>>  Subject: Re: ACTION 2001-11-02#02: Datatyping use-cases from CC/PP
>>
>>
>>  >......
>>  >It appears to me that we have two separate issues here:
>>  >
>>  >1. The association of data type to literal.
>>  >2. The prescriptive/descriptive nature of data types.
>>
>>  Can you enlarge on that second point? I have no idea what you mean,
>>  and it doesn't seem to have come up before.
>>
>>  For what its worth, I have always assumed that RDF is basically a
>>  descriptive language, so if 'prescriptive' is somehow in contrast to
>>  descriptive then I might take umbrage.
>>
>>  Pat
>
>There was discussion about this a few weeks ago in the
>rdf-interest list (or was it rdf-logic...?)
>
>Anyway, the gist is that if both a local type and a range
>are defined, then the range can be seen as prescriptive such
>that a value can be deemed invalid if the local type is
>not equivalent to or a subclass of the range type.

Thanks, but I still don't know what you are talking about. What does 
it mean to say that a value is 'invalid'? The way I see RDF is that 
triples make assertions. More triples make more assertions, which 
restrict the set of satisfying interpretations. There is no notion of 
some part of a triple being 'invalid': if you can write it down, then 
it ought to mean something. (If some construction is meaningless then 
we should rule it out as syntactically illegal; but there is a strong 
RDF cultural bias against this kind of restriction, for 
methodological reasons having to do with the 'open-ness' of the 
semantic web. )

>If no local type is defined for the value, then the range
>can be seen as descriptive of the type of the value.
>
>The latter is all fine and good, until we think about lexical
>forms and the fact that lexical forms are specific to a
>given data type, and thus, the descriptive approach is not
>reliable as it may suggest an interpretation for which the
>lexical form is either not valid or "unknown".

Well, it can be unknown: that is harmless. I agree that we need some 
security against *incorrect* interpretations being used on literals, 
so they are interpreted in ways that are not the way intended.

Pat
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Received on Wednesday, 7 November 2001 15:53:34 EST

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