xsl:attribute : node already has children

here is what I am getting now:

xsltproc --timing --stringparam collect.xref.targets "only" --stringparam targets.filename "tdb-pile.xml" pile.xsl impnotes.xml
Parsing stylesheet pile.xsl took 23 ms
Parsing document impnotes.xml took 9642 ms
Xref is only supported to listitems in an orderedlist:
runtime error: file /usr/share/docbook-xsl/common/titles.xsl line 657 element attribute
xsl:attribute : node already has children
runtime error: file /usr/share/docbook-xsl/common/titles.xsl line 657 element attribute
xsl:attribute : node already has children
Writing tdb-pile.xml for book(impnotes-top)
Applying stylesheet took 226404 ms
no result for impnotes.xml
make: *** [tdb-pile.xml] Error 9
xsltproc --timing --stringparam collect.xref.targets "only" --stringparam targets.filename "tdb-chunk.xml" chunk.xsl impnotes.xml
Parsing stylesheet chunk.xsl took 0 ms
Parsing document impnotes.xml took 7938 ms
Xref is only supported to listitems in an orderedlist:
runtime error: file /usr/share/docbook-xsl/common/titles.xsl line 657 element attribute
xsl:attribute : node already has children
runtime error: file /usr/share/docbook-xsl/common/titles.xsl line 657 element attribute
xsl:attribute : node already has children
Writing tdb-chunk.xml for book(impnotes-top)
Applying stylesheet took 261702 ms
no result for impnotes.xml

what does this mean?!

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