How to Message Framework available in ISA ?

Hi,

I am new to ISA. I am trying to get acquainted with the Message Framework used in ISA to post error,info and warning messages. The details given in dev & Extn guide was not adequate to give it s start off. I have searched through the forums but couldn't find any.

Please do guide me (thinking of a beginner) in achieving this understanding, so that i could populate my own customized error messages in JSP and guide subsequent flow after having shown the same.

Thanks,

Abhi