PurposeElectronic Data Interchange (EDI) and Application Link Enabling (ALE) are used for exchanging business data between different systems.For both these forms of communication, you require the IDoc Interface. The IDoc interface is made up of the definition of a data structure and the processing logic of this data structure. The data structure is the IDoc. The IDoc is the general exchange format of the communicating systems. IDocs can be sent using different methods (for example,  RFC or as a file).

Application Link Enabling (ALE)You distribute data using ALE if you want to communicate from one system to one or more other (mostly internal) systems. ALE transfers data in IDoc format and uses the methods of tRFC for data transfer.

       ALE enables the integration of business processes across several SAP or non-SAP systems.

Electronic Data Interchange (EDI)You use EDI if you want to exchange business application documents with an (external) partner system (for example, a customer or vendor). The SAP system sends EDI messages in IDoc format to an EDI subsystem, where they are converted to a universal EDI standard (UN/EDIFACT or ANSI/X12). This enables communication with non-SAP systems.

       By definition, two partners are involved in the process in an EDI application scenario: The sender and the recipient of an EDI message. 

Distribution of application data between R/3 Systems with different releases

Data exchange can continues after an upgrade without any further adjustment

Customer-specific enhancements The integration of non-SAP systems through communication interfaces Coupling R/3 and R/2 Systems