Modular Verification: Testing a Subset of Integrated Modular Avionics in Isolation

Integrated modular avionics (IMA) present many benefits in power and weight savings for an aircraft, but also create new challenges for verification due to the increased complexity in interactions between the highly integrated network of avionics systems. For a large set of hosted avionics functions, it is impractical to exhaustively test an entire set of functions while they are fully integrated. There can be a combinatorial explosion of test cases for an integrated IMA system since the performance and function of a hosted system can be impacted by other hosted systems. This traditional test approach would be characterized by a high cost of change since any single system change could require the full integrated set of systems to be retested. This paper introduces a modular verification strategy for IMA systems, which provides a practical approach to verifying these architectures. Within the modular verification strategy, systems are verified in isolation from the fully integrated set of avionics systems. This can be done without requiring re-test within the fully integrated environment. In order to accomplish this, terms of equivalency must be established for an avionics system's test environment with respect to the integrated system environment. This equivalency relies on reasoning in the logical system domain rather than the physical system domain. This is a fundamental change in reasoning from traditional verification concepts employed within federated architectures. The cost of change is minimized since each hosted system can be tested and retested without impacting the test results for other hosted systems. This proposed verification strategy is based upon the author's experience in developing the Genesis IMA architecture at Smiths Aerospace. The Genesis IMA architecture was implemented on the Boeing 787 Dreamliner as the common core system (CCS). The CCS is one of the first implementations of an "open systems" IMA architecture