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Re: toward a minimal datatypes spec: hmm...

From: Dan Connolly <connolly@w3.org>
Date: 02 Aug 2002 08:47:04 -0500
To: Graham Klyne <Graham.Klyne@MIMEsweeper.com>
Cc: w3c-rdfcore-wg@w3.org
Message-Id: <1028296026.28231.216.camel@dirk>

On Fri, 2002-08-02 at 05:17, Graham Klyne wrote:
> At 01:58 AM 8/2/02 -0500, Dan Connolly wrote:
> >---
> >:rangeSyntax a r:Property;
> >   s:range :Datatype.
> >
> >@prefix log: <http://www.w3.org/2000/10/swap/log#> .
> >
> >this log:forAll :P, :L, :DT.
> >
> >{ [] :P :L.
> >   :P :rangeSyntax :DT.
> >} log:implies { [] :DT :L }.
> >
> >:rangeSyntax s:comment { # example...
> >   { ex:age :rangeSyntax dt:integer.
> >     ex:jenny ex:age "10" }
> >     log:implies { [] dt:integer "10" } }.
> >---
> 
> Maybe I'm missing something here,

I confused you with the use of [] in the premise
and the conclusion; they're not the same variable.

> but what if there are two such properties?:
> 
>    [] :P1 :L1 ;
>       :P2 :L2 .
>    :P1 :rangeSyntax :DT1 .
>    :P2 :rangeSyntax :DT2 .
> 
> then doesn't that also give us:
> 
>    [] :DT1 :L1 ;
>       :DT2 :L2 .

no, it gives
	[] :DT1 :L1.
	[] :DT1 :L2.

Each [] is a different existentially quantified variable.
Perhaps the rules is more clearly written:

{ :S :P :L.
   :P :rangeSyntax :DT.
} log:implies { _:something :DT :L. this log:forSome _:something }.

> ?
> 
> I'm thinking there may be problems with things like:
> 
>    :Jenny :age "10" ;
>           :weight "70" .
> 
> leading to something like this:
> 
>    :Jenny :integer "10" ;
>           :integer "70" .

no, it just gives
	_:x :integer "10".
	_:y :integer "70".

> >So I'm starting to wonder if it makes more sense
> >to specify datatypes in terms of some of the WebOnt
> >features... or move some WebOnt features
> >into RDFS or something...
> 
> Hmmm... that has a ring of sense to it.  I read that as suggesting a full 
> account of datatypes really belongs at a higher layer.  I still think 
> there's a case for a strictly local handling of datatypes in RDF, as in:
> 
>     :Jenny :age _:x .
>     _:x :integer "10" .
> 
> but I think that doesn't depend on anything in RDF that isn't already 
> there, other than a convention for naming XML schema datatypes with URIs, 
> and interpreting them as RDF properties.

But are there *any* consequences to this convention?

> I can also see merit in Guha's suggestion, which I see as effectively being 
> a way to distinguish literal datatypes syntactically and extending the 
> domain of graph literals to include non-strings.  I think that's similar to 
> what others have asked for, to parallel what happens in most programming 
> languages.

Yeah... functional terms, even a limited f(l) form, where
f is a URIref and l it a literal, are appealing.


> As a long-time proponent, I agree that global datatyping can be very useful 
> -- but I'm just not convinced we collectively know enough to do it properly 
> at this time.
> 
> The tough question, I think, is whether we need to commit to tidy literals 
> throughout at this time,

I find that question easy to answer, in the affirmative.

> or is there a way to leave an escape hatch for 
> future developments?  For example (adapting Guha's suggestion, and 
> reverting to XML):
> 
>     <rdf:Description about="http://example.org/Jenny">
>        <ex:age>10</ex:age>
>     </rdf:Description>
> 
> would not actually specify anything semantically beyond
> 
>     < I(http://example.org/Jenny), x > in IEXT(I(ex:age)), for some x
> 
> but something like:
> 
>     <rdf:Description about="http://example.org/Jenny">
>        <ex:age xsi:type="xsd:string">10</ex:age>
>     </rdf:Description>
> 
> or
> 
>     <rdf:Description about="http://example.org/Jenny">
>        <ex:age xsi:type="xsd:decimal">10</ex:age>
>     </rdf:Description>
> 
> would force the tidy interpretation that you use in your work.

This sort of design is only interesting to me if xsi:type
defaults to string.

> There are still questions about the form of the abstract graph (ack. 
> Jeremy) -- I can imagine a couple of possibilities, but I don't think 
> they're as hard to solve as what we've been trying to do.
> 
> #g
> 
> 
> -------------------
> Graham Klyne
> <GK@NineByNine.org>
-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
see you in Montreal in August at Extreme Markup 2002?
Received on Friday, 2 August 2002 09:46:39 EDT

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