A mapping is implemented by a mapping program. You use a mapping program to define:
How structure nodes (or elements) in the source structure are assigned to structure nodes in the target structure
Usually, elements with the same semantic meaning are assigned to each other. This part of the mapping is usually referred to as structure mapping.
How the source element is transformed into a value target element
SAP NetWeaver Process Integration supports the use of different kinds of mapping programs:
Message mapping
With a message mapping, you map one message type to another by using a graphical editor in the ES Repository. A mapping program is generated from the graphical design.
Java program and XSLT (Java) program
These mapping programs are developed in Java and XSLT (eXtensible Stylesheet Language Transformations) respectively, and imported into the ES Repository as an archive.
XSLT (eXtensible Stylesheet Language Transformations) is a language that enables you to convert an XML document to another document. You can develop mappings with XSLT and import them to the ES Repository.
ABAP program and XSLT (ABAP) program
These mapping programs are developed using the ABAP Workbench. At runtime, these programs are executed on the ABAP Engine of the Application Server on which the Integration Server is running.
These kinds of mapping programs cannot be imported into the ES Repository and therefore are not shipped by SAP. They have to be developed in the SAP system at the customer's site.
For usability reasons, it makes sense to design message mappings because you can use the graphical editor.