automated keywords and chunking

Hi,
I'm using DocBook 5 and the html chunking stylesheets. I'd like to  
automatically create keywords for each output file that consist of the  
primary index terms in that file.  I can manage that in postprocessing  
using Python and lxml, but I wanted to ask here to see if this has  
been done before. It seems like something people might like to do, but  
after looking at the chunking code and reading about it, it sounds  
like it might be pretty complicated to implement.

Any ideas on this?
thanks,
--Tim Arnold