You extend an app's Gateway layer when you need to expose additional back-end logic and content to the UI layer. In SAP NetWeaver Gateway Service Builder (transaction SEGW), redefine the relevant Gateway service for the app.
To get the name of your BSP application, refer to the application-specific documentation. There you can also find the SEGW project or OData Service name.
Refer to SAP Note 1919388 for details of how to extend an OData service.
Using this approach leads to runtime artifacts where the Customer Data Provider Class (DPC) class is a subclass of the SAP-delivered class.
You can check this by examining the superclass of the Customer’s DPC classes.
To avoid collisions between customer-specific and SAP-specific names, ensure you create the names in the customer namespace. Alternatively, use prefixes, such as Y or Z. This is relevant for OData properties, entity types, navigation properties, associations, entity sets, and method.