Pete Cordell wrote:
[...]
 > If neither of these are OK, then from what I've heard on this list,
 > you'll need something like Schematron to impose the constraints (I'm
 > afraid I haven't had the chance to get round to using it myself.)

Here it is a working example of XML Schema with embedded Schematron 
rules to check that the type value matches the message element.

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" 
elementFormDefault="qualified"
   xmlns:sch="http://www.ascc.net/xml/schematron">
   <xs:element name="test">
     <xs:complexType>
       <xs:sequence>
         <xs:element maxOccurs="unbounded" ref="message"/>
       </xs:sequence>
     </xs:complexType>
   </xs:element>
   <xs:element name="message">
     <xs:annotation>
       <xs:appinfo>
         <sch:pattern name="Check that the type matches the element.">
           <sch:rule context="message[event]">
             <sch:assert test="type='Event'">The type for event should 
be 'Event'.</sch:assert>
           </sch:rule>
           <sch:rule context="message[contact-information]">
             <sch:assert test="type='Contact'">The type for 
contact-information should be
             'Contact'.</sch:assert>
           </sch:rule>
         </sch:pattern>
       </xs:appinfo>
     </xs:annotation>
     <xs:complexType>
       <xs:sequence>
         <xs:element ref="type"/>
         <xs:choice>
           <xs:element ref="contact-information"/>
           <xs:element ref="event"/>
         </xs:choice>
       </xs:sequence>
     </xs:complexType>
   </xs:element>
   <xs:element name="type" type="xs:NCName"/>
   <xs:element name="contact-information">
     <xs:complexType>
       <xs:sequence>
         <xs:element ref="address"/>
       </xs:sequence>
     </xs:complexType>
   </xs:element>
   <xs:element name="address">
     <xs:complexType/>
   </xs:element>
   <xs:element name="event">
     <xs:complexType>
       <xs:sequence>
         <xs:element ref="stuff"/>
       </xs:sequence>
     </xs:complexType>
   </xs:element>
   <xs:element name="stuff">
     <xs:complexType/>
   </xs:element>
</xs:schema>


On a sample document like

<?xml version="1.0"?>
<test>
   <message>
     <type>Event2</type>
     <event>
       <stuff/>
     </event>
   </message>

   <message>
     <type>Contact2</type>
     <contact-information>
       <address/>
     </contact-information>
   </message>
</test>


It will give:

SystemID: C:\george\workspace\oXygen\samples\test.xml
Location: 3:0
Description: The type for event should be 'Event'. (type='Event')

SystemID: C:\george\workspace\oXygen\samples\test.xml
Location: 10:0
Description: The type for contact-information should be 'Contact'. 
(type='Contact')

Best Regards,
George
---------------------------------------------------------------------
George Cristian Bina
<oXygen/> XML Editor, Schema Editor and XSLT Editor/Debugger
www.---.com




From ht@i... Tue Feb 14 09:38:25 2006
Received: from maggie.w3.org ([193.51.208.68])
	by frink.w3.org with esmtp (Exim 4.50)
	id 1F8w