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Re: Input sought on datatyping tradeoff

From: Brian McBride <bwm@hplb.hpl.hp.com>
Date: Fri, 12 Jul 2002 09:40:26 +0100
Message-Id: <5.1.0.14.0.20020712091419.061cd1a0@15.144.25.13>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: www-rdf-interest@w3.org

At 19:24 11/07/2002 -0400, Peter F. Patel-Schneider wrote:
>Unfortunately, I think that this request is incorrectly formulated.

Oh dear.  And I tried so hard to be both clear and correct :(

>   I
>think this for several reasons.
>
>1/ The request does not mention some of the unusual aspects of XML
>Schema datatypes, such as union datatypes and the ability to override
>the normal typing of literals in union datatypes.  The presence of
>these unusual features in XML Schema datatypes makes them much harder
>to handle.

You are correct that the question does not mention these.  For now we have 
only been considering primitive XML schema datatypes.  If you could show 
that these other datatypes steer the decision decisively in one direction 
or the other, that would be a great contribution.


>2/ The request begs question A by using semantically-loaded terms,
>like ``ageInYears''.  This is only partly alleviated by stating that
>the answer must be the same for question A, A2, and A3.  It would be
>much better to use a property, like rdf:object, that does not have a
>natural range type that is associated with it.  If rdf:object is not
>used, then some other property without such as strong natural range
>type should be used instead, perhaps even one like
>``ageInYears-or-title''.

The use of these "semantically-loaded" terms is intended to make the issue 
clear to folks without getting into mathematics.  I want input from folks 
who would be put off by a technical mathematical discussion.  A3 for 
example, is intended to get folks to ask themselves whether they really 
think of the <ageInYears> property as denoting an integer or a string.

I take your point about using rdf:object though I'm leery of that because 
we could (I believe would) get ourselves tangled up in issues around the 
semantics of reification which would obscure rather than clarify the issue.

I agree with you though, that we should make the point to folks that an rdf 
processor doesn't know <ageInYears> from <uuid:a;lskdjalkjd>.



>3/ The request contains a number of unsupported assertions, including
>``[t]he answer must be the same for all three of these A tests'' and
>``[i]t is not possible to have the ansewrs to Tests A and Test D both
>be yes.''  I think that these assertions need justification.

I agree we owe an explanation of these assumptions.  I surely wish we could 
square the circle and remove these constraints.  RDFCore has struggled with 
datatypes for many months now.  We have not yet found a way and believe we 
are forced into making this choice.

I'd be happy to review with you how we got here and will start a thread on 
rdf-logic for that purpose.


>4/ The request does not describe the implications of answers, except
>that as yes to Question A must also be a yes to Questions A2 and A3.
>There are many implications of the answers to these questions, and
>responses by responders who are not aware of the implications may
>change if the responders are made aware of the implications of their
>responses.

What implications do you have in mind?


>5/ The request does not indicate why other attractive solutions to
>datatypes are not being considered.  One such solution would be to
>require that all literals be types, perhaps by using xsi:type
>constructs.

Please could you construct a short description of this idea and send it to 
rdf comments.


>I request that the request be reformulated to address my concerns and
>then resent to the mailing lists.

I am hopeful that the request as formulated will lead to useful input to 
the WG and would like to press ahead with it as is.  In particular, I am to 
get input from the wider community, including, but not only, from those who 
don't have a PhD in mathematical logic.  DPH, please speak up.

Brian
Received on Friday, 12 July 2002 04:41:38 GMT

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