two elements with the same name but different types

From: andrew welch <andrew.j.welch@gmail.com> Date: Mon, 20 Mar 2006 11:55:43 +0000 Message-ID: <74a894af0603200355q7563a3dcg2350500fd40f6e34@mail.gmail.com> To: xmlschema-dev@w3.org

Hi,

I'm trying to model the following in a schema:

<head>
  <title>the title<title>
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
  <meta name="fixed_1" content="variable"/>
  <meta name="fixed_2" content="variable"/>
  <meta name="fixed_3" content="variable"/>
  <meta name="fixed_4" content="fixed_5"/>
</head>

Here the first <meta> has two fixed value attributes, then the
following three have fixed name attributes (which are all different
fixed values) but any content attributes.  The last meta contains two
fixed value attributes, like the first.

Is this possible to model with XML Schema?  Currently I have:

<xs:element name="head">
  <xs:complexType>
    <xs:sequence>
      <xs:element ref="title"/>		

      <xs:element name="meta">
        <xs:complexType>
          <xs:attribute name="http-equiv" type="xs:string"
fixed="Content-Type"/>
          <xs:attribute name="content" type="xs:string"
fixed="text/html; charset=utf-8"/>
        </xs:complexType>
      </xs:element>

      <xs:element name="meta">
        <xs:complexType>
	  <xs:attribute name="name" type="xs:string" fixed="fixed_1"/>
          <xs:attribute name="content" type="xs:string"/>
        </xs:complexType>
      </xs:element>

      <xs:element name="meta">
        <xs:complexType>
          <xs:attribute name="name" type="xs:string" fixed="fixed_2"/>
          <xs:attribute name="content" type="xs:string"/>
	</xs:complexType>
      </xs:element>

....
      <xs:element name="meta">
        <xs:complexType>
          <xs:attribute name="name" type="xs:string" fixed="fixed_4"/>
          <xs:attribute name="content" type="xs:string" fixed="fixed_5"/>
	</xs:complexType>
      </xs:element>

I read that this is ok as long as the element definitions are local
and not global, but I still get the error:

"two elements with the same name <meta> but different types appear in
the content model"

The other problem is defining when "fixed_4" is the value for the name
attribute, "fixed_5" must be the value for the content attribute. 
Isn't this a co-occurrence constraint?  In which case it's not
possible to do this in XML Schema...?

I'm writing this schema within an <xsl:import-schema> element in XSLT
2.0, so it's not possible to use Relax NG here.  This is to validate
the output as it's being generated by the transform... the alternative
is to do the validation as a seperate step in the pipeline, which
might be the only option....

thanks
andrew


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