PRB: "Schema Is Non-Deterministic" Error Message When You Add XSD to XMLSchemaCache Object (316297)

MORE INFORMATION

Sample Nondeterministic XSDs

• Sample 1: People.xsd

  <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" 
             targetNamespace="urn:People" xmlns="urn:People" elementFormDefault="qualified">
  
    <xs:element name="people" type="PeopleData"/>
  
    <xs:complexType name="PeopleData">
      <xs:sequence>
        <xs:element name="person" type="persondata" minOccurs="0" 
        maxOccurs="unbounded"/>
        </xs:sequence>
    </xs:complexType>
  
    
    <!-- 
  Explanation: The content model of the personData complexType is non-deterministic.
  This is an example of the ((b, c) | (b, d)) non-deterministic content model with a small difference.
  In this sample, the second sequence lists three elements and is of the form ((b,c) | (b,d,c)).
  The XML processor must look ahead to determine the matching sequence when it encounters b.
  This requirement to look ahead makes the content model non-deterministic.
    --> 
   
  
    <xs:complexType name="persondata">
     <xs:choice>
      <xs:sequence>
        <xs:element name="first_name" type="xs:string"/>
        <xs:element name="last_name" type="xs:string"/>      
      </xs:sequence>
      <xs:sequence>
        <xs:element name="first_name" type="xs:string"/>
        <xs:element name="middle_name" type="xs:string"/> 
        <xs:element name="lastname_name" type="xs:string"/> 
      </xs:sequence>
     </xs:choice>    
    </xs:complexType> 
  
  
   <!-- 
  Solution: Use a (b,(c | (d,c))) content model.
   
   <xs:complexType name="persondata">
     <xs:sequence>
      <xs:element name="first_name" type="xs:string"/>
      <xs:choice>
        <xs:element name="last_name" type="xs:string"/>                
        <xs:sequence>      
          <xs:element name="middle_name" type="xs:string"/> 
          <xs:element name="lastname_name" type="xs:string"/> 
        </xs:sequence>
      </xs:choice>    
     </xs:sequence>
   </xs:complexType>
    -->
  
  </xs:schema>
  					

• Sample 2: Catalog.xsd

  <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" 
             targetNamespace="urn:Catalog" xmlns="urn:Catalog" elementFormDefault="qualified">
  
    <xs:element name="catalog" type="CatalogData"/>
  
    <xs:complexType name="CatalogData">
      <xs:sequence>
        <xs:element name="book" type="bookdata" minOccurs="0" 
        maxOccurs="unbounded"/>
        </xs:sequence>
    </xs:complexType>
  
  
    <!-- 
  Explanation: The content model of the bookdata complexType is non-deterministic.
  The title elements in both of the sequences that are defined for the choice element have a minOccurs property setting of 0.
  The processor cannot determine the matching sequence when a title element is not present in the XML instance document
  (possibly because the minOccurs property of the element is set to 0).
    --> 
  
  
    <xs:complexType name="bookdata">
  
     <xs:choice>
      <xs:sequence>
        <xs:element name="author" type="xs:string"/>
        <xs:element name="title" type="xs:string" minOccurs="0"/>      
      </xs:sequence>
      <xs:sequence>
        <xs:element name="title" type="xs:string" minOccurs="0"/>
        <xs:element name="author" type="xs:string"/> 
      </xs:sequence> 
      </xs:choice> 
    
    </xs:complexType>   
  
  
    <!-- 
  Solution: This content model definition for the bookdata complexType specifies
  that the author element and the title element can occur in any order in the XML instance document,
  and that the presence of the title element is optional. 
  
  The same requirement can be specified using an all element as shown in the following definition. 
    
    <xs:complexType name="bookdata">
      <xs:all>
         <xs:element name="author" type="xs:string"/>
         <xs:element name="title" type="xs:string" minOccurs="0"/>  
      </xs:all> 
    </xs:complexType name="bookdata">
    --> 
  
  
  </xs:schema>
  					

Steps to Reproduce Behavior

1. Use Notepad to create and save the People.xsd sample schema document in the root folder of your hard disk.
2. Open a new Standard EXE project in Visual Basic 6.0.
3. Add a project reference to Microsoft XML, v4.0.
4. Drag a command button to Form1.
5. Paste the following code in the Click event procedure of the command button:

   Dim sc As MSXML2.XMLSchemaCache40
   Set sc = New MSXML2.XMLSchemaCache40
   
   sc.Add "urn:People", "c:\people.xsd"
   					

6. Save and then run the project. Click the command button when the form is displayed.
7. Use the following definition for the personData complexType in the commented Solution section of sample 1 to replace the active definition:

   <xs:complexType name="persondata">
      <xs:sequence>
       <xs:element name="first_name" type="xs:string"/>
       <xs:choice>
         <xs:element name="last_name" type="xs:string"/>                
         <xs:sequence>      
           <xs:element name="middle_name" type="xs:string"/> 
           <xs:element name="lastname_name" type="xs:string"/> 
         </xs:sequence>
       </xs:choice>    
      </xs:sequence>
    </xs:complexType>
   					

8. Save the changes to the schema document and try to add the XSD to the MSXML 4.0 XMLSchemaCache object by re-executing the Visual Basic code. Note that the schema is added successfully and that no errors messages are displayed.

#import <msxml4.dll>