Implementing Inbound Processing 
This section describes the implementation of an ALE-enabling interface for inbound IDocs. The prerequisite is that message types and IDoc types have already been defined.
Components of an ALE interface for processing inbound IDocs
A complete ALE interface for the processing of inbound IDocs consists of:
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1. A function module to process inbound IDocs. The ALE layer calls the function module.
2. An SAP Business Workflow task with objects and events for error handling.
3. ALE table entries (‘settings’).
Processing an inbound IDoc
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1. ALE reads the inbound IDoc customizing settings to determine which function module to call.
2. The function module is called and given the IDoc(s) to be processed.
3. The function module returns status information about whether the IDoc was successfully processed.
4. If it was successfully processed, it returns the ID of the application document that was created or changed.
5. If an error occurred while processing the IDoc, the ALE layer triggers the SAP Business Workflow event assigned to the IDoc.
See also:
· Objects, Events and Tasks To Be Created
· Inbound Processing Using SAP Workflow
· Advanced Workflow Programming