The tangible benefits of EDI include: applied to build up an interchange. Less manual data entry leading to an increased accuracy. The building blocks start with data elements, which map onto 2. Reduced clerical overheads resulting in a lower cost base. familiar data items such as part number. 3. Faster delivery of data allowing shorter lead times and even These are combined to form segments which are groups of related enabling lower stock levels with consequent cost savings. elements e.g. name and address. Some syntaxes allow compound elements and compound segments. Segments are used to build EDI messages (also known as transac- tion sets in ANSI X12). A message is analogous to a document such 38.2 EDI in the messaging marketplace as a purchase order. Finally messages are grouped together in batches for transmission The marketplace for EDI goods and services has been operating for and this is known as an interchange. some time but it is only since November 1990 that a complete OSI Interchanges for all the main EDI standards include the concept standard for moving EDI messages over the OSI stack has been fully of a header containing special segments to pass control information ratified. To understand how this standard, X.435, was arrived at a about the sender, recipient, date/time and a reference number. brief history of the messaging marketplace is included with an Whilst many data elements are alike in the three main EDI outline of the X.400 standard used for inter personal messaging standards (EDIFACT, ANSI X12, TRADACOMS), the main dif- (IPM). ferences lie in the characters used to separate fields, the definitions The area of messaging has been the most active area for standards of segments and messages. work over the past couple of years. This may well be because it takes As mentioned above the process of defining specific messages has about six years from the recognition of a business need to the been community, even industry, driven. So whilst EDI messages provision of standards based products to fit the r