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2 questions about the definition of 'cn'

From: Michael Hucka <mhucka@caltech.edu>
Date: Fri, 22 Apr 2005 19:39:02 -0700
Message-ID: <17001.46406.950650.300732@dhcp-222.cds.caltech.edu>
To: www-math@w3.org

There are two oddities about the definitino of 'cn' in the
MathML schema that I'm hoping other people can help me
understand.  I'm referring here to the schema available at

1. The definition of 'cn' allows empty content.  In
   content/tokens.xsd, there is the following:

    <xs:complexType name="cn.type" mixed="true">
      <xs:group ref="cn.content" minOccurs="0" maxOccurs="unbounded"/>
      <xs:attributeGroup ref="cn.attlist"/>
    <xs:element name="cn" type="cn.type"/>
   However, it is not clear to me what meaning this would
   have.  It is also not clear to me that the MathML spec
   itself allows empty content in 'cn' elements.  (Does it?)

2. The definition of 'cn' content is the following:

    <xs:group name="cn.content">
        <xs:group ref="Presentation-expr.class"/>
        <xs:element ref="sep"/>
   Looking up 'Presentation-expr.class', we find that it is
   defined in common/math.xsd as (perplexingly):

    <xs:group name="Presentation-expr.class">
        <xs:group ref="PresExpr.class"/>
        <xs:group ref="ContExpr.class"/>

   This appears to me to allow unrestricted MathML content
   to be present as the content of a 'cn' element.  However,
   according to section of the MathML-20031021
   spec, it seems that the only content that should be
   allowed are character sequences possibly separated by

Are my interpretations of MathML and/or the XML Schema
incorrect?  I'd appreciate any feedback.


Mike Hucka, Ph.D. Senior Research Fellow   mhucka@caltech.edu 
Control and Dynamical Systems 107-81       tel: +1.626.395.6911
Caltech, Pasadena, CA 91125, USA           fax: +1.702.554.3067
Received on Saturday, 23 April 2005 02:39:11 UTC

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