- From: James Clark <jjc@jclark.com>
- Date: Sat, 27 Apr 2002 08:11:51 +0700
- To: Ashok Malhotra <ashokma@microsoft.com>, noah_mendelsohn@us.ibm.com
- cc: XML Schema Comments <www-xml-schema-comments@w3.org>
> I'm sorry you are troubled but consider this case.
>
> <xsd:simpleType name="myTime">
> <xsd:restriction base="xsd:dateTime">
> <xsd:pattern
>
> value="[0-9]{2}:[0-9]{2}:[0-9]2.[0-9]*(Z|[+-]?[0-9]{2}:[0-9]{2})?."/>
> </xsd:restriction>
> </xsd:simpleType>
>
> What is the value space and lexical spece of the derived type and how
> are they related?
I would make a couple of observations here:
- Defining a data type requires not just defining the lexical and value
spaces, but also defining the mapping from the lexical space to the value
space. There's no way in XML Schema for a user to specify a new
lexical-to-value space mapping. The only lexical-to-value-space mappings
available are those associated with the builtin primitive types. The
lexical-to-value-space mapping of the derived type is always the
lexical-to-value-space mapping of the base type.
- Specifying a derived type with a pattern facet does NOT specify that the
lexical space of the derived type is equal to the set of strings matched by
the pattern regex. Rather it specifies that the lexical space is the
intersection of that set of strings with the lexical space of base type.
This ensures that the lexical space of the derived type is always a subset
of the lexical space of the base type, which in turn guarantees that the
lexical-to-value-space mapping of the base type remains suitable for the
derived type.
James
Received on Friday, 26 April 2002 21:09:37 UTC