You want to use the xpointer function in an xinclude statement in DocBook 5.0 and resolve the xinclude with xmllint.

Example 1, “Bad xinclude example” is a typical xinclude statement that would have worked correctly with DocBook 4.x.

<!-- This is INCORRECT -->
<xi:include xmlns:xi="http://www.w3.org/2001/XInclude"
    href="filename.xml"
    xpointer="xpointer(//title[1])"/>
      

However, with DocBook 5.0, this statement will not work correctly because xpointer sees a reference without a namespace, but the included file is in the DocBook namespace (http://docbook.org/ns/docbook). Therefore, xpointer won't recognize the contents of filename.xml.

Give the xpointer statement the namespace of the included file. Example 2, “Good xinclude example” shows how to do this:

<xi:include xmlns:xi="http://www.w3.org/2001/XInclude"
    href="filename.xml"
    xpointer="xmlns(db=http://docbook.org/ns/docbook)xpointer(//db:title)"/>
      

Namespaces are powerful constructs, but they require attention to detail, especially when you move from a non-namespaced to a namespaced environment.