Process 
Process
External interfaces are designed solely in external maintenance transactions (abbreviation: external maintenance). You define how data fields are distributed on the screens of this maintenance transaction. The only restriction is that fields belonging to one view always have to be put together on a data screen since there is a common function module for each view that is used to check data (event After input).
The function modules defined for the BDT events are used to read data from the database as well as to check the data and save it. External maintenance determines the current data prior to output using the function modules that read the data (see
Tables).External maintenance and BDT maintenance can be fully integrated. You can call BDT maintenance in transfer mode from external maintenance. Data can be changed in both types of maintenance. Changes are also visible in each type of maintenance. When making the transition from one kind of maintenance to the other, the data is flagged in the global memory of the application function groups.
The BDT provides varying function modules that are called in external maintenance (procedure described in detail in the chapter
BDT Function Modules). These modules in turn process one or more BDT events, which calls event modules in the applications.Multiple BDT application objects can be maintained at once in external maintenance.
Note: In order to be able to work with external interfaces, it is very important that you adhere to the specifications given by the developer for the required actions in events. Correct reading and correct supply of the current and global memory in events ISDAT, DTAKE, DSAVC and DSAVE are particularly important.
Example: External interfaces are used in IBU Utilities to maintain move-in documents. A business partner and a contract account, among other objects, are maintained using the maintenance transactions for move-in documents (transactions EC50, EC51 and EC52).