EDI 101 \ How does it work?

EDI is implemented in software and is conceptually an interface between the sender's and the receiver's internal computer programs. These company specific internal programs may be operating on different types of computers and may use different internal data structures. This interface between sender and receiver is implemented in at least the two trading partners systems, and often in a third, intermediary.

We'll use the transmission of a purchase order to illustrate how EDI works. The buying party's purchase order system generates a PO and passes it to the EDI software. The EDI software converts the internal data structure into a standard EDI transaction with the required fields supplied by the data dictionary. This transaction is then transported to the supplier whose EDI software converts (using the same data dictionary) the standard transaction into the format acceptable to their order processing system.

The TDCC and other vendors provide EDI software for mainframes, mini, and personal computers. The TDCC leases mainframe software written in ANSI COBOL and is shipped on 9 track tape. TDCC provides the COBOL source code because few mainframe COBOL systems are exactly alike. The user may need to make some changes to the software to match their particular system.

The TDCC software is “table-driven.” This means that all translations between internal and standard data formats are defined in easily modifiable tables. You do not have to modify COBOL programs for translation. A portion of the EDI software, called the Set Generator, converts internal format records into standard transactions. These internal format records are produced by some internal system such as a Purchase Order System. The Set Generator reads these input records and performs the translation according to the parameter tables and the information in the data dictionary.

When the transactions are received by the destination EDI software, the receiver's data dictionary and parameter tables are used by the Set Interpreter to convert the standard format transaction into the desired internal format.