Need help interpreting an error output

Hi,

wenn I run the following command for my docbook5 (relaxng) documents:

xsltproc --xinclude --output Test.html /usr/share/xml/docbook/xsl-ns-stylesheets-1.79.2/
html/docbook.xsl darktable.xml  

I get following error output:

ERROR: xref linking to export_selected has no generated link text. Error: no ID for 
constraint linkend: "export_selected". ERROR: xref linking to lighttable_chapter has no 
generated link text. Error: no ID for constraint linkend: "lighttable_chapter". ERROR: xref 
linking to import has no generated link text. Error: no ID for constraint linkend: "import". 
ERROR: xref linking to export_selected has no generated link text. Error: no ID for 
constraint linkend: "export_selected". Error: no ID for constraint linkend: 
"image_information". ERROR: xref linking to collect_images has no generated link text. 
Error: no ID for constraint linkend: "collect_images". ERROR: xref linking to 
recently_used_collections has no generated link text. Error: no ID for constraint linkend: 
"recently_used_collections". ERROR: xref linking to selected_images has no generated link 
text.

*What does it exactly mean?*


./lighttable/panels/geotagging.xml:    xml:id="geotagging"> ./lighttable/panels/
geotagging.xml:  <sect3 xml:id="geotagging_usage"> 


./map/map.xml:      <keyword>geotagging</keyword> ./map/map.xml:      (see <xref 
linkend="geotagging"/>).



Thanks for your help
Pierre