An Application Building Block (ABB) can either be a stand-alone application (e.g. material maintenance) or a smaller part of an application (e.g. long text or classification maintenance) which is integrated into the Service Provider Infrastructure (SPI). To create an own Application Building Block for a smaller part of an application especially makes sense if that part can be reused by multiple applications. Otherwise it is advisable not to split an application into several Application Building Blocks.
To uniquely identify an Application Building Block an ID needs to be defined (along with the Service Provider and Metadata Provider class names) via view /PLMB/V_SPI_ABB.
Whenever a SPI based application is accessed, either by instantiating a Connector or by using the FPM SPI Integration (FSI) the Application Building Block ID (ABBID) is a mandatory import parameter to identify the application that is to be instrumented.
A tutorial on how to define an Application Building Block ID can be found in the tutorials section.