A service interface is defined as a series of operations. In each operation, you create service interface fields that correspond to your COBOL program's entry point fields. At runtime, data is sent between the service and the program via these fields.
In COBOL, you describe a data item's data type precisely, using its picture clause. Java uses its own set of data types. The Interface Mapper enables you to create mappings between the COBOL types in your program and the types available in Java.
We'll use the Interface Mapper to define streamlined access to our program by defining an operation for each of the program's four possible actions - Read record, Add record, Delete record, and Get next record. Each operation will require the client to send just the data needed by that particular operation.