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Re: Cannes entailment, a question:

From: pat hayes <phayes@ai.uwf.edu>
Date: Tue, 25 Jun 2002 10:26:08 -0500
Message-Id: <p05111b07b93e3abb28c0@[65.217.30.113]>
To: Jan Grant <Jan.Grant@bristol.ac.uk>
Cc: w3c-rdfcore-wg@w3.org

>On Tue, 25 Jun 2002, pat hayes wrote:
>
>>
>>  >in two parts.
>>  >
>>  >One, for symmettry, where a literal "really is" a string,
>>
>>  Well, that question is now moot, since a literal is *never* a string.
>>  A literal is a 3-tuple. Thus:
>>
>>  >do we have an
>>  >analagous situation to the Cannes entailment?
>>  >
>>  >	eg:book dc:title "the big book of RDF" .
>>  >
>>  >entails...
>>  >
>>  >	eg:book dc:title _:a .
>>  >	_:a xsd:string "the big book of RDF" .
>>
>>  No, that cannot possibly be valid. The thing inside those quotes is
>>  either not a string or not a literal. Im not yet quite sure which is
>>  correct: maybe its neither of them.
>
>Hang on, you've spotted the get-out (that the thing in quotes is a
>Literal, but not an xsd:string), but given that I fail to see why the
>above entailment should not hold.

Because the value of dc:title can always be chosen to not be an 
xsd:string and still satisfy the first triple. Those interpretations 
will block the entailment.

>Unless the datatyping proposal gives a
>uniform treatment to _all_ xsd datatypes, I can't see how we can vote in
>favour of it.

Well, I agree. If the literals in the graph really are 3-tuples, then 
ALL of the datatyping debate - all of which was under the false 
assumption that literals were items in datatype lexical spaces, ie 
strings - has been rendered moot. We simply don't have datatyping in 
RDF graphs, with these literals: it's meaningless. The 3-tuple 
<1,"10","french"> isn't in the lexical space of any XSL datatype.

>If we have to accept non-regularity in datatyping then
>there are far simpler approaches that support the xsd types "natively"
>and other types using a daml-like construct that seem much more natural.

I'd like to know the details of them. We have considered the daml 
ideas before, at length, and they were resoundingly rejected by the 
WG.

Pat


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Received on Tuesday, 25 June 2002 11:26:11 EDT

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