Clarification on Backdoor Event Engine

Hi all,
I just wanna clarify that , is the backdoor event engine(which does all
    the signature detection) eventually invokes the corresponding event
    engine and the Analyser .

    For example let me take SSH , when the ssh packet is recevied
    the libpcap , the backdoor event engine will be th e one which
    the packet first , based on the signatures invokes the ssh event
    and the ssh event engine invokes the Policy scripts which contain
    event handlers/analysers ..finally log the data to the file.

    Please correct me if my understanding is wrong.