input Directory and File formats

Hey! I'm trying to write a program which will output a set of messages 
that can be used by MHonArc.  For example...

My Program
 |
 | output
 V
set of message files
 |
 | input
 V
MHonArc
 |
 | output
 V
archives


Where can I find the specs for the file formats and directory structure 
that My Program would need to output?

- Greg