(1) (Serial Peripheral Interconnect) See SPI bus.
(2) (Stateful Packet Inspection) See stateful inspection.
(3) (Service Provider Interface) The programming interface for developing Windows drivers under WOSA. In order to provide common access to services, the application (query, word processor, e-mail program, etc.) is written to a particular WOSA-supported interface, such as ODBC or MAPI, and the developer of the service software (database manager, document manager, print spooler, etc.) writes to the SPI for that class of service.