msgmain
msgmain — The primary component of a message in a message set
Description
Every Msg must have one primary message. This is stored in the MsgMain. The primary message is distinguished from any number of submessages (MsgSub) or related messages (MsgRel) that a Msg might have.
Processing expectations
Formatted as a displayed block.
On the whole, the semantics of MsgSet are not clearly defined.