HL Hierarchical Level
To identify dependencies among and the content of hierarchically related groups of data segments
A unique number assigned by the sender to identify a particular data segment in a hierarchical structure
HL01 shall contain a unique alphanumeric number for each occurrence of the HL segment in the transaction set. For example, HL01 could be used to indicate the number of occurrences of the HL segment, in which case the value of HL01 would be "1" for the initial HL segment and would be incremented by one in each subsequent HL segment within the transaction.
Identification number of the next higher hierarchical data segment that the data segment being described is subordinate to
HL02 identifies the hierarchical ID number of the HL segment to which the current HL segment is subordinate.
Code defining the characteristic of a level in a hierarchical structure
HL03 indicates the context of the series of segments following the current HL segment up to the next occurrence of an HL segment in the transaction. For example, HL03 is used to indicate that subsequent segments in the HL loop form a logical grouping of data referring to shipment, order, or item-level information.
Code indicating if there are hierarchical child data segments subordinate to the level being described
HL04 indicates whether or not there are subordinate (or child) HL segments related to the current HL segment.