A procedure for designing abstract interfaces for device interface modules

This paper describes the abstract interface principle and shows how it can be applied in the design of device interface modules. The purpose of this principle is to reduce maintenance costs for embedded real-time software by facilitating the adaptation of the software to altered hardware interfaces. This principle has been applied in the Naval Research Laboratory's redesign of the flight software for the Navy's A-7 aircraft. This paper discusses a design approach based on the abstract interface principle and presents solutions to interesting problems encountered in the A-7 re-design. The specification document for the A-7 device interface modules is available on request; it provides a fully worked out example of the design approach discussed in this paper.