Problem with xi:include of section

I'm trying to include a section from one document into another document.

In the source file, the xi:include is:

<xi:include href="ref_config_object_json.xml" xpointer="config-obj-dashboard" xmlns:xi="http://www.w3.org/2001/XInclude" />

This resolves correctly in the XML editor.

When I try to build the document (we use the Docbkx Maven plugin), the build fails, with the following error:

org.xml.sax.SAXParseException; systemId: file:///Users/janicem/Documents/sqrrl/doc/src/xml/dat_sqrrl_ui_dashboard_configure.xml; lineNumber: 192; columnNumber: 128; Include operation failed, reverting to fallback. Resource error reading file as XML (href="" Reason: XPointer resolution unsuccessful.

Error on line 192 column 128 of file:///Users/janicem/Documents/sqrrl/doc/src/xml/dat_sqrrl_ui_dashboard_configure.xml:

Error reported by XML parser: An 'include' failed, and no 'fallback' element was found.

Error on line 62 column 90 of file:///Users/janicem/Documents/sqrrl/doc/src/docbkx/SqrrlDataMgmtAnalysis.xml:

  Error reported by XML parser: Error attempting to parse XML file (href="">

Error on line 174 column 68 of file:///Users/janicem/Documents/sqrrl/doc/src/docbkx/SqrrlGuides.xml:

  Error reported by XML parser: Error attempting to parse XML file (href="">

After looking at the DocBook docs, I tried adding a DOCTYPE entry with the DTD, but that didn't work either.

So is this xpointer syntax just not supported in this case? Or am I just missing some other setting?

Thanks,

Janice