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Re: XML Schema WG comments on RDF documents

From: C. M. Sperberg-McQueen <cmsmcq@acm.org>
Date: Fri, 14 Mar 2003 16:38:21 -0700
Message-Id: <>
To: pat hayes <phayes@ai.uwf.edu>
Cc: w3c-rdfcore-wg@w3.org, www-rdf-comments@w3.org, w3c-xml-schema-ig@w3.org

At 2003-03-14 12:00, pat hayes wrote:
>Thanks for your comments on the RDF semantics document.
>I will adopt your editorial suggestions, correct typos, and will try to 
>remove uses of terminology with any potential philosophical penumbra from 
>the technical prose in the document.
>I have one clarification question concerning your comment on datatypes:
>3.2. Types as lexical mappings (schema-related)
>       A datatype is an entity characterized by a set of character strings
>       called lexical forms and a mapping from that set to a set of
>       values.
>     We have a couple of reservations concerning this characterization.
>      * The statement describes (with the exception of the problem just
>         noted) simple datatypes, but not the class of complex datatypes
>         which can be defined by XML Schema, nor all the types (or
>         type-like constructs) definable in various other schema languages
>         for XML.
>I have followed other authors in this characterization, and am somewhat 
>surprised to discover that it is incomplete or inadequate. Can you 
>suggest, or point me to a source for, a definition which does cover the 
>more general case, or which clarifies what is wrong with this 
>characterization? We are supposed to have a datatyping framework which can 
>handle all the built-in XML Schema datatypes.

Members of the Schema WG have pointed out that the spec actually
doesn't use 'datatype' as a term for complex types, so the comment
we sent you is not quite right.  Some members of the WG, including
the individual who actually drafted that comment, think of the
term 'datatype' as denoting a class with two major subclasses,
the simple and the complex (data)types; on that interpretation, the
description in the RDF semantics document describes only the simple
types, but not all datatypes.  The XML Schema spec, it would appear,
may well stop short -- and almost certainly does, though I have not
checked this question in preparing this reply -- of committing the
WG or the reader to that as an official view.

If one does not think that the superclass common to complex types
and simple types is usefully called 'datatype', then (a) one has
some good company in some members of the XML Schema WG, and (b) the
description in RDF Semantics would appear to be unobjectionable.

At the moment, I'm speaking only for myself; I will put the question
to the WG in a future meeting and ask for a clarification, revision,
or retraction of the comment in question.

Thank you for your request for clarification; it promises to be
enlightening for a larger number of us than might at first have been

-C. M. Sperberg-McQueen
Received on Friday, 14 March 2003 19:03:34 UTC

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