Standard SAP sends out or receives in data through IDocs using standard delivered Segments, Message Types and fields. But sometimes, these fields are not sufficient for a specific end-to-end business scenario as far as data transfer is concerned. So in such scenarios, we can add new segments with completely new structures to the standard IDoc as an extension. We create a brand new structure and insert it into existing delivered IDoc structure creating a whole new IDoc satisfying the requirement. This new IDoc is called an Extended IDoc
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An IDoc is the run−time instance of an IDoc type. An IDoc consists of a control record, several data records,and a list of status records. The control record defines control information such as sender and receiver information. The data records contain the application data that is to be transferred via IDocs. The status records contain status information (success or failure) recorded at each point in the process.
A large enterprise’s networked computing environment is likely to connect many geographically distributed computers to the main database. These computers are likely to use different hardware and/or operating system platforms. An IDoc (for intermediate document) encapsulates data so that it can be exchanged between different systems without conversion from one format to another. IDocs are used for for electronic data interchange (EDI) between application programs written for the popular SAP business system or between an SAP application and an external program. IDocs serve as the vehicle for data transfer in SAP’s Application Link Enabling (ALE) system.
Many people think of MVC design pattern as a means for separating data presentation from data processing, and this is certainly true. However, the separation of data presentation from data processing is only one use case of a much more fundamental concept — namely, the separation of those parts of the program that generate data from those parts that consume data — and it is this fundamental principle that you see time and again within the Web Dynpro architecture.