An IDoc consists of a control record with the structure edidc and one or more data records with the structure edidd. The control record is similar to a letter envelope. It contains the sender and receiver of the IDoc, as well as information on the type of message. The data that is being used by the IDoc is contained in the data records as unformatted character strings.

To be able to pass an IDoc to the ALE layer, you must set up a field string with the structure edidc and an internal table with the structure edidd. With these the function module master_idoc_distribute is then called. The module saves the data to the database and if necessary triggers despatch.

All ALE message flows are stored in the ALE distribution model. The distribution model is the central controlling instance for ALE. The application can interrogate the distribution model before the IDoc is created. This makes sense if the actual creation of an IDoc influences the application. As you are not required to set up the internal table for the IDoc if no message flow is maintained in the distribution model, it can also improve performance.

The ALE layer always interrogates the distribution model. If the application does not specify a receiver, all receivers are determined and an IDoc is created for each one. If the application does specify a receiver, a check is made against the distribution model to see whether the receiver has the necessary authorization. In ALE you can use the filter settings in the distribution model to remove parts of the IDoc.