XInclude Schema/Namespace Problem?

Question

I'm trying to use XML Includes to help manage a large XML structure that needs to be usable by both humans and machines.

But am experiencing a myriad of problems when trying to construct XML files that can be validated against an existing schema. Here's a simplified example of what I'm trying to do.

My "main.xml" file does not validate.

<?xml version="1.0" encoding="UTF-8"?>
<!-- Main.xml - This fails to validate. -->
<ns1:main xsi:schemaLocation="http://www.example.com/main main.xsd"
          xmlns:ns1="http://www.example.com/main"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xmlns:xi="http://www.w3.org/2001/XInclude"&gt;

    <name>String</name>
    <xi:include href="child.xml"/> <!-- What I'm trying to do. -->

</ns1:main>

The "child.xml" file validates fine as a standalone file.

<?xml version="1.0" encoding="UTF-8"?>
<!-- Child.xml - This validates fine, as a standalone file. -->
<ns1:child xsi:schemaLocation="http://www.example.com/main main.xsd"
           xmlns:ns1="http://www.example.com/main"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"&gt;

    <name>String</name>
    <age>String</age>

 </ns1:child>

Here's my schema:

 <?xml version="1.0" encoding="UTF-8"?>
 <!-- Main.xsd - My Simplified Schema -->
 <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
            xmlns:ns1="http://www.example.com/main"
            targetNamespace="http://www.example.com/main"&gt;

    <!-- Main Element (References Child) -->
    <xs:element name="main">
         <xs:complexType>
             <xs:sequence>
                 <xs:element name="name" type="xs:string"/>
                 <xs:element ref="ns1:child"/>
             </xs:sequence>
         </xs:complexType>
    </xs:element>

    <!-- Child Element -->
    <xs:element name="child">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="name" type="xs:string"/>
                <xs:element name="age" type="xs:string"/>
            </xs:sequence>
        </xs:complexType>
     </xs:element>

</xs:schema>

My issues are almost-obviously related to namespaces but I'm at a loss for how to fix my problem.

Answer 1

I don't think the XML Schema and XInclude specifications are guaranteed to be compatible with each other. Individual XML processors might allow it, but others will not.

As a general rule, I'd say that the two should not be used together.

P.S. I'm not sure why you think this is a namespace problem. What gives you that impression?

Answer 2

As skaffman already pointed out, XML Schema and XInclude are not compatible.

The validation error message from xmllint states this clearly:

main.xml:9: element include: Schemas validity error : Element  '{http://www.w3.org/2001/XInclude}include': This element is not expected. Expected is ( {http://www.example.com/main}child ).
main.xml fails to validate

To quote the W3C Recommendation: "XInclude defines no relationship to the augmented infosets produced by applying an XML schema. Such an augmented infoset can be supplied as the input infoset, or such augmentation might be applied to the infoset resulting from the inclusion."

Thus you should first construct the whole XML file by applying the XIncludes, and validate this file afterwards.

Edit: You can use xmllint with --xinclude to validate main.xml.