On attach, a module must register its function tables with OCSF by calling CSSM_RegisterServices. Its function tables consist of a table of module management function pointers, plus one table of Service Provider Interface (SPI) function pointers for each (service, subservice) pair contained in the module. The module management functions include Initialize, EventNotify, and Terminate. The interface functions reflect the OCSF API for each security service. The function prototypes and their descriptions provide the OCSF SPI specifications. If a subservice does not support a given function in its SPI, the pointer to that function must be set to NULL. These structures are specified in the OCSF header files, cssmspi.h, cssmtpi.h, cssmcli.h, and cssmdli.h.