EDI Interchange definition and structure
EDI Interchange is a structured according to the X12 rules data set which companies sent to each other via EDI. EDI Interchange means more than a simple document – it is a documents package (though sometimes it can contain only one group with one document). We will use the term EDI document when speaking about Interchange, or simply document regarding a separate document (transaction set). EDI Interchange begins with ISA segment and ends up with IEA (ISA/IEA Envelope). ISA is used also for document routing between partners.
X12 defines each EDI document as a set of segments and elements which determine this particular document, confirms the segment consequence in a document, the elements consequence in a segment as well as relationships between segments and/or elements. X12 standard assigns a special name and number for each separate document – 810 Invoice, 850 Purchase Order, 856 Ship Notice/Manifest.
EDI Interchange structure
An interchange may consist of the following segments:
UNA Service String Advice Conditional*
UNB Interchange Header Mandatory
UNG Functional Group Header Conditional**
UNH Message Header Mandatory
User data segments
UNT Message Trailer Mandatory
UNE Functional Group Trailer Conditional**
UNZ Interchange trailer Mandatory
* Mandatory if EDItEUR recommendations are followed.
** Not used in EDItEUR applications.
Segments starting with “UN” are called service segments. They constitute the envelope or the “packaging” of the EDIFACT messages. The UNA segment defines the separator characters used in the transmission, if they are not the default set for the character set defined in the UNB segment. The UNB segment identifies the sender and receiver of the transmission, specifies the character set used, and carries other “housekeeping” data for the transmission. The UNG and UNE segments are used only if the transmission carries several groups of messages of different types. EDItEUR strongly recommends that a transmission should be limited to carrying only one group of messages of a single type. The UNG and UNE segments are not, therefore, used in EDItEUR practice. The UNZ segment ends the transmission. The UNA, UNB and UNZ segments will normally be generated in outgoing transmissions, and processed in incoming transmissions, by a standard EDI software package. The user application need not be aware of their content. However, many implementers prefer to generate the whole of the EDIFACT transmission file as part of their own application software.