[xslt] xsltproc &XInclude

[philippe coq <philippe coq objectweb org>]

I haven't succeed to process a docBook document that contains XInclude  directives:
I have the following:

1) DocBook document xx.xml:
<?xml version="1.0" encoding="UTF-8"?>
<section>
  <title />
<xi:include href=""
              xmlns:xi="http://www.w3.org/2001/XInclude" />
</section>

2) DocBook document xx1.xml:
<section>
  <title/>
  <para>The services are:</para>
   <variablelist>
    <varlistentry>
      <term>registry:</term>
      <listitem>
        <para>It is automatically launched
        before all the other services when starting <xi:include
        href="" xmlns:xi="http://www.w3.org/2001/XInclude"
        xpointer="appserver" />.</para>
      </listitem>
    </varlistentry>
 </variablelist>
</section>
3) Document variables.xml:
<section>
  <title>Variables used</title>
  <para><phrase id="appserver">JOnAS</phrase></para>
</section>

I process with the following script:
xsltproc --xinclude  -o $OUTPUTDIR/xx.html $XSLDIR/html.xsl xx.xml

I have the following error:
xx1.xml:16: element include: XInclude error : could not load variables.xml, and no fallback was found

the variables.xml file is located in the same directory than XX.xml and xx1.xml.

I am using
xsltproc -version
Using libxml 20627, libxslt 10117 and libexslt 813
xsltproc was compiled against libxml 20626, libxslt 10117 and libexslt 813
libxslt 10117 was compiled against libxml 20626
libexslt 813 was compiled against libxml 20626

Have I missed something?

Thanks,
Philippe