Attempting to connect XML files with Xinclude attribute xml:base error

Question

I wouldn't be here if I hadn't Googled my way into Oblivion. I have the following problem: I have an XML Schema, 3 single XML documents, and an XML document to link all of the other 3. I am running into the following error and I do not understand why.

E [Xerces] cvc-complex-type.3.2.2: Attribute 'xml:base' is not allowed to appear in element 'SoftwareRequirementsDocument'.

I have read a bunch of forum posts from Google with people with a similar problem but none of their fixes would help me. I will post my Schema, 1 XML document to be connected, and the XML document with XInclude. I will post the beginning of each document as that is what is needed.

Here is NotionalSchema2.xsd:

<xsd:element name="ProjectLifecycleDocuments" type="ProjectLifecycleDocumentsType"/>
<xsd:complexType name="ProjectLifecycleDocumentsType">
    <xsd:choice minOccurs="0" maxOccurs="unbounded">
        <xsd:element ref="Team"/>
        <xsd:element ref="SoftwareRequirementsDocument"/>
        <xsd:element ref="UseCaseDocument"/>
        <xsd:element ref="TestCaseDocument"/>
    </xsd:choice>
    <xsd:attribute name="id" use="required" type="xsd:ID"/>
</xsd:complexType>

<xsd:element name="SoftwareRequirementsDocument" type="SoftwareRequirementsDocumentType"/>
<xsd:complexType name="SoftwareRequirementsDocumentType">
    <xsd:sequence>
        <xsd:element ref="Section" maxOccurs="unbounded"/>

        <!-- Other global elements to be referenced here. -->
    </xsd:sequence>
    <xsd:attribute name="projectName" use="required" type="xsd:string"/>
    <!--<xsd:attribute name="id" use="required" type="xsd:ID"/>-->
</xsd:complexType>

Here is my NotionalSRS2.xml:

<SoftwareRequirementsDocument projectName="Lifecycle Documents with Requirements  
Tracking" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xsi:noNamespaceSchemaLocation="NotionalSchema2.xsd"      
xmlns:xx="http://apache.org/xml/features/xinclude/fixup-base-uris">

    <Section id="RQ1.0">

    <Title>Introduction</Title>
  <Para>The Software Requirements Specification details the extent of NUWC’s Lifecycle Project Manager. The product’s main feature is it’s ability to create and manage lifecycle documents using a graphical user interface. The lifecycle documents will be organized and exported using an XML Schema. This can be accomplished by a user who has no knowledge of the XML language. This document will review all the basic functionality required for a user to edit, create, and manage lifecycle projects.
  </Para>    
    </Section>

    <Section id="RQ1.1">
        <Title>Purpose</Title>
        <Para> To provide a detailed description of how the product will produce it’s lifecycle documents as well as edit and export them. It also overviews the basic functional requirements requested by the customer.
        </Para>
    </Section>

And here is my file using XInclude, ProjectLifecycleDocuments.xml :

<ProjectLifecycleDocuments id="PL1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-     
instance" xmlns:xi="http://www.w3.org/2001/XInclude"
xsi:noNamespaceSchemaLocation="NotionalSchema2.xsd">
<xi:include href="NotionalSRS2.xml"/> 

</ProjectLifecycleDocuments>

Now I read a lot about namespacing when searching this error, but I could not get a clear grasp on where I was going wrong.

If you could point me in the right direction as to why this error is happening and how I can approach fixing it, that would be great.

Answer 1

The xml:base attribute (W3C XML Base is added by XInclude for compliance with the specification. See: http://xerces.apache.org/xerces2-j/faq-xinclude.html#faq-3

The FAQ proposes two solutions. One of them requires you to disable the insertion of the xml:base attribute by setting a feature when running the parser. The other consists on configuring your schema to allow the xml:base attribute in the included type, which you can do by importing the XML XSD in your schema:

<xsd:import namespace="http://www.w3.org/XML/1998/namespace" schemaLocation="http://www.w3.org/2001/03/xml.xsd" />

And then declaring the attribute with a reference to xml:base:

<xsd:complexType name="SoftwareRequirementsDocumentType">
    <xsd:sequence> ... </xsd:sequence>
    <xsd:attribute name="projectName" use="required" type="xsd:string"/>
    <xsd:attribute ref="xml:base"/>
    ...
</xsd:complexType>