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Re: Values without lexical forms (xmlsch-04 your 2.2)

From: Jeremy Carroll <jjc@hpl.hp.com>
Date: Fri, 11 Apr 2003 20:32:48 +0300
To: cmsmcq@acm.org, www-rdf-comments@w3.org
Message-Id: <200304112032.48975.jjc@hpl.hp.com>


Hi

I am finally getting round to your comments about the RDF Concepts and 
Abstract Syntax document.

There is one I find particularly surprising.

Our text:
[[
Each member of the value space may be paired with any number
        (including zero) of members of the lexical space
]]

I understand your suggestion as to change "(including zero)" to "greater than 
zero".

You said:
[[
The lexical space of any simple datatype in XML Schema
    is the domain of the type's lexical mapping; the value space is its
    domain.
]]

If I remember correctly, the reason we have the unexpected "including zero" is 
because of our understanding of XML Schema Union datatypes.
Hence I am seeking clarification.
I have asked the WG just now for other reasons why we have this text; but I 
don't believe there are.

So XML Schema example:
=====================

<xsd:element name="foo">
  <xsd:simpleType>
    <xsd:union memberTypes="xsd:string xsd:int"/>
  </xsd:simpleType>
</xsd:element>

The lexical space of the first type masks the lexical space of the second. 
Thus no integers have a corresponding lexical form.

Then the lexical mapping maps no values to the integer 2, but it is in the
value space since
   <foo xsi:type="xsd:int">2</foo>

conforms with this type, and accesses the hidden part of the value space.

(My XML Schema is weak - I am sure I have made a number of errors, but the
objective should be clear enough)

Please help me understand where I have gone wrong.

Jeremy
Received on Friday, 11 April 2003 14:32:32 GMT

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