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Re: comment on current deliberations in RDF Core concerning the lexical space of XML Schema datatypes

From: pat hayes <phayes@ihmc.us>
Date: Fri, 12 Sep 2003 23:45:43 -0700
Message-Id: <p06001f0bbb87b5f9925f@[]>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: w3c-rdfcore-wg@w3.org

>I see several claims in the RDF Core WG mailing list archives to the effect
>that the lexical space of XML Schema datatypes is not well-defined.
>However, when I look at http://www.w3.org/TR/xmlschema-2/, I see very
>specific definitions of the value space of XML Schema datatypes.  For
>example http://www.w3.org/TR/xmlschema-2/#decimal states
> Lexical representation
>	decimal has a lexical representation consisting of a finite-length
>	sequence of decimal digits (#x30-#x39) separated by a period as a
>	decimal indicator. If totalDigits is specified, the number of
>	digits must be less than or equal to totalDigits. If
>	fractionDigits is specified, the number of digits following
>	the decimal point must be less than or equal to the
>	fractionDigits. An optional leading sign is allowed. If
>	the sign is omitted, "+" is assumed. Leading and trailing zeroes
>	are optional. If the fractional part is zero, the period and
>	following zero(es) can be omitted. For example: -1.23,
>	12678967.543233, +100000.00, 210.
>This appears to me to be completely well-defined.  In particular, leading
>and trailing spaces are *NOT* allowed in the lexical representation of the
>XML schema decimal datatype.

I agree that this reads unambiguously. Unfortunately there is also 
other wording in the same document which suggests an alternative 
interpretation: to wit, the inclusion of the whiteSpace facet as a 
constraining facet on xsd:integer, which is meaningless if one 
understands the above text strictly in the way you suggest.  And even 
more regrettably, there is ample evidence in the text of the document 
that it is not intended to be read quite so strictly, viz. it is 
internally incoherent if so read.  Overall, therefore, I think that 
the situation is ambiguous, or at least underdetermined. In any case, 
we have decided to ask the XSD WG to rule on the matter and will 
include a test case illustrating their ruling.

>NB: In XML Schema whitespace processing is performed before any checking of
>     whether a string belongs to a lexical space.  Thus any aspect of
>     whitespace processing is irrelevant to the question of what strings
>     belong to the lexical space of an XML Schema datatype.

This might affect the test case, however, which is written in XML.


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Received on Saturday, 13 September 2003 02:45:27 UTC

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