Software Engineering Institute

This TSP Symposium 2014 presentation describes an architecture-led incremental assurance strategy throughout the development life cycle to address the challenges of certifying mission- and safety-critical systems that have become increasingly software reliant. This strategy is pursued in an international SEI, industry, and government collaboration. For aircraft, software as percentage of total system cost has grown from 33% in 1997 to 67% in 2010, with verification-related software rework cost alone exceeding 50%. Systems are currently verified against ambiguous, incomplete, and inconsistent requirements. Industry studies show that 70% of embedded software system defects are introduced in requirements and architecture design, while 80% are discovered post-unit test, with rework cost as much as 300–1,000 times the cost of in-phase correction.

The strategy involves a paradigm shift from build-then-test to an architecture-centric engineering approach that utilizes analytical virtual system integration based on the SAE Architectural Analysis & Design Language standard to discover problems earlier in the life cycle. This paradigm shift is being pursued by an international aerospace industry initiative known as System Architecture Virtual Integration, with return on investment studies showing major cost savings.

The strategy measurably improves requirement coverage through architecture-led requirement specification—incorporating operational requirements such as performance, timing, safety, reliability, and security—and systematically addressing hazards in the process. The strategy applies contract-based compositional verification one architecture layer at a time to ensure that requirements are addressed throughout the life cycle. Finally, the strategy incrementally manages an assurance plan and its execution throughout the life cycle, producing assurance case artifacts for certification.