The X12 series of standards consist of a number of interdependent standards. The transaction set standards define the grouping of data into segments and the sequence of these segments to be used in a specified business transaction such as a purchase order. There are also the 'foundation' standards which define the syntax to be used in defining X12 transaction sets as well as the data elements, data segments, and control structures to be used. The full set of foundation standards required to interpret, understand and use the X12 series of transaction set standards, consists of:

• Data element dictionary (X12.3)
• Interchange control structure (X12.5)
• Application control structure (X12.6)
• Data Segment Directory (X12.22)
• Security Structures (X12.58)