Electronic Data Interchange
The Interchange (ASC/X12)

The Interchange is the outside envelope of an EDI document.  It is the structure that contains the start of business information to begin the trade exchange.  This envelope is initiated by the interchange header (ISA) and terminated by an interchange trailer (IEA), and wraps the functional groups.  Additionally, in the context of the interchange structure, there are control segments that extend the envelope to provide additional services to process the interchange.  Currently, these control segments are:

• The Grade of Service (ISB).
• The Deferred Delivery Request (ISE).
• The Interchange Delivery Notice (TA3).
• The Interchange Acknowledgment (TA1).

The above interchange control segments must occur in the order shown above should they be present in the interchange structure.  The interchange acknowledgment (TA1) is followed by the functional groups if any exists.

• The Interchange Header
• The Interchange Trailer