how to use Bro getting 41 features of a connect record

  I am doing my research work in Intrusion Detection System. I read
a paper about abnormal detection technique by CS Columbia
University. An clustering algorithm is applied to cassify the normal
and abnormal connections. Connections has higher level than packets
which is used in snort, so connection can have less data size and
more infomation.
  The author said Bro is modified to generate the 41 features, I
would preciated if someone is kind enough to give me some hints how
to do this. I am sure a event analyser and handler sould added to
Bro, but where, how and when to invoke the event handler.

   Anderson Lee