EDI Basics

Interchange Control Envelope [ISA/IEA]

In simple terms an interchange is a smallest unit of exchanged data between two parties. It is important to mentioned that a received or sent file may contain one or more interchanges, but from an EDI point of view each of these interchanges will be handled separately.

Interchange control envelope consists of two segments. The ISA or header segment and the IEA or envelope trailer segment. These two segments are related and contain information to link them together.

ISA Segment

The ISA segment is probably the most important segment because it contains details on how to parse the rest of the file. Unlike any other segment in X12, ISA is fixed length. This allows for processing software to identify delimiters for parsing the rest of the segments. Also, since it is the beginning of an message it is the segment that the processing software seeks to determine the beginning of the message and and separate data from garbage characters that sometime can be found during communication (extra spaces before and after and between EDI messages).

The ISA Segment has the following structure

ISA Segment
  ISA01 Authorization Information Qualifier
  ISA02 Authorization Information
  ISA03 Security Information Qualifier
  ISA04 Security Information
  ISA05 Interchange ID Qualifier
  ISA06 Interchange Sender ID
  ISA07 Interchange ID Qualifier
  ISA08 Interchange Receiver ID
  ISA09 Interchange Date
  ISA10 Interchange Time
  ISA11 Interchange Control Standards ID
  ISA12 Interchange Control Version Number
  ISA13 Interchange Control Number
  ISA14 Acknowledgement Requested
  ISA15 Test Indicator
  ISA16 Subelement Separator
                   

IEA Segment

The IEA Segment has the following structure

ISA Segment
  IEA01 Number of Included Functional Groups
  IEA02 Interchange Control Number (same as ISA13)