Envelope types

This documentation describes the ways in which envelope types are used.

Envelope types are used for these reasons:

To specify the syntax objects in the interchange that follows (the UNA).
To surround messages or functional groups of an interchange (the UNB and UNZ).
To surround a set of messages of the same type (the UNG and UNE).
To surround the body of a message (the UNH and UNT).

Each Envelope type begins with a set of letters that identifies the segment, for example UNA. These same sets of letters (UNA) are also used in the Properties window of the Type Designer to define the value of the initiator.