EDI document transmission uses a system of three “envelopes” to house your transaction sets – Message envelope, Group envelope and Interchange envelope.
Just as paper business documents are sent in envelopes and it’s possible to mail many documents in a single envelope, EDI documents are exchanged using several envelopes.
- Each Transaction Set is placed in its individual envelope
- A group of transaction sets – e.g. a group of purchase orders – is placed in a group envelope. (The group envelope is mandatory in ANSI and optional in EDIFACT.)
- All group envelopes being sent from one sender to one receiver are placed in an Interchange envelope
See the diagram below:
An envelope is formed by a pair of segments that define the beginning and end of the appropriate section. Using the EDIFACT standard as the example, the Transaction Set Envelope uses the UNH and UNT segments, the Group Envelope uses the UNG and UNE segments and the Interchange Envelope uses the UNA/UNB and UNZ segments. In each case, the “S” indicates the “start” of the envelope and the “E” indicates the “end” of the envelope. The diagram below illustrates the three levels of envelopes that would surround a single EDI purchase order.