Continue with your activities in the SAP Business Suite backend system.
In transaction SE24 create a new ABAP OO class which inherits interfaces from the abstract class /IWBEP/CL_MGW_ABS_DATA as data provider class (DPC).
In this example we use /IWBEP/CL_MGW_RT_SFLIGHT.
Redefine and implement all methods of interface /IWBEP/IF_MGW_APPL_SRV_RUNTIME that are needed for the service.
Activate your class.
Continue with 1.3. Register your Model / Service.