Electronic Form Structure (868) is used to define and communicate the schema, rules, and structure of EDI transactions and data elements. Trading partners—typically standards bodies, software vendors, or system administrators—send this transaction set to receivers who need to understand or implement EDI message formats. The transaction is often transmitted in response to requests for technical specifications or as part of standardization initiatives. Key segments include the E01 (Electronic Form Main Heading), which identifies the overall form being described; the E20 (Segment Header Information) loop, which details individual segments within a transaction set; and the E30 (Data Element Attributes) loop, which specifies the characteristics, requirements, and valid values for data elements.

For example, a standards development organization such as the American Standards Committee might send an 868 transaction to software development companies implementing X12 purchase order processing. The transmission could contain an E01 heading identifying it as the structure for the 850 (Purchase Order) transaction, followed by multiple E20 loops describing each required segment (such as BEG for beginning segment details, REF for references, and PO1 for line items). Within each E20 section, nested E30 loops would define the data elements themselves—specifying whether a field is mandatory or optional, its data type, length restrictions, and in the E34 sub-loop, a list of valid codes (for example, all acceptable unit-of-measure codes). This structured information allows receiving organizations to validate incoming purchase orders and configure their EDI systems correctly.