Incremental Life Cycle Assurance of Safety-Critical Systems

Finding problems and optimal designs in the requirements phase is more efficient than later phases. However, over-constraining the solution is also sub-optimal since not all information is necessarily available upfront. 'Build-then-test' approaches which insist on developing first requirements, then architecture, then implementation are not suitable for building systems that must be rapidly fielded and respond to ever-changing demands. Our approach, ALISA, is working on integrating four pillars for incrementally building systems which can be shown to satisfy the relevant requirements. Our four key pillars for assuring requirements satisfaction are requirements specifications, architecture models, verification techniques, and assurance case traceability between the first three. In this paper we introduce our approach, and highlight how we are integrating these pillars using an XText-driven DSL and tool meta-model leveraging existing tools and languages. Our current focus is on understanding exactly which requirements are responsible for the majority of design constraints. Identifying this subset promises to reduce architecture design space exploration and verification overhead, increasing delivery cadence.