Thanks a lot,
Am I right that all I need to activate your code to experiment with is to install these 3 modules (and possibly those which are involved in those 3)?

I also ran into Ted Pedersen site but did not understand whether it only does statistical analysis or can solve my entire problem.

Actually what I want is to split text into meaningful parts and then I can filter only those which are real keywords for the subject using Classification which I am good at.

One last question is: I can't figure out how to activate sending e-mail notifications to my private e-mail address when I got a forum reply.