s sought SO a means of making new technology more immediately The 'movement' standards, building on the previous work available is clearly required. which established the OSI seven layer model and defined the To achieve such a target it is necessary to distinguish between the lower levels up to transport (Level 4), these now take the model principles involved and the actual protocols. to the application layer, Level 7. Historically the U.K. EDI marketplace has been dominated by the 2. The 'message' standards, work done to define the content, use of VANS with a high degree of added value on the network. The layout and data sets which are then moved over the above. This added value has taken the form of verification of the data set, is the traditional realm of EDI and leads to definitions of EDI security and trading relationship checking, translation services be- 38/4 Electronic data interchange ON-NET PROCESS Figure 38.1 Network value added tween data sets and to some extent communications protocol con- seen as the ideal vehicle to further the completion of the OSI model, version. perhaps as it was a fairly easy concept to grasp. The communications prevalent have been proprietary or at best de So the second wave of E-mail products were able to convert the facto, either IBM protocols or OFTP (albeit over X.25). Whilst the principles of the proprietary systems into the 1984 X.400 protocols Edifact syntax is standardised the number of registered international to give an OSI solution to the E-mail requirement. This is now being standard messages is relatively small. Most recognised messages refined to the 1988 X.400 model which gives a much closer match relate to smaller industry groups and are awaiting international to the 7 layer model. This is because it splits the application down ratification. and actually uses layers 5 and 6 properly instead of being a complete To fully understand the emergence of OSI standards for EDI it is application (layers 5, 6 and 7 in one) sitting on layer 4 as the 1984 necessary to take 