T2 Message ID in Response

A very basic question, but in looking through the 1.0 spec,
email threads, and issues log, I can't find an answer.

MessageID uniquely identifies a message
RefToMessageID references that unique MessageID to identify
a message that an ack, status request / response, etc.
relates to.

My assumption is that the sending MSH generates the unique
MessageID (based on the critera of RFC 2392).  Does the
receiving MSH use the same MessageID for the response, or
does it generate a new, unique MessageID for the response
message and use the RefToMesageID to indicate that it is a
response to the sending MSH Message?

I think the spec requires some text somewhere to clarify, or
it could be interpreted a couple of ways.

Colleen


--
Colleen Evans
Principal Product Manager
Sonic Software Corporation
phone:  720 480-3919 or 303 791-3090
email:  
http://www.sonicsoftware.com