Understanding Hierarchical Loops

Hierarchical loops defined in EDI transactions or messages are considered the most complex structures in the EDI processing environment. Hierarchical loops define different levels of data, which can be used in any sequence, and skipped if the information is not needed. This allows EDI messages to align the loop to the data.

A Hierarchical loop is simply a special kind of nested loop where the nesting is not physically defined in the EDI transaction, but rather in the data content of the hierarchy. Successive occurrences of a hierarchical show a parent - child relationship.

The X12 856 transaction set is used to describe a physical shipment as well as information relating to the shipment, such as order information, product description, physical characteristics, type of packaging, marking, carrier information, and configuration of goods within the transportation equipment.

The X12 856 HL segment is used to define the start of a hierarchical looping structure. The HL segment must be created for each node of the application data hierarchy.