Achieving high integrity at low cost: a constructive approach

Abstract

The paper presents a development process, delivering high-quality software at exceptionally low cost, and its application to the mission computer software for the new Lockheed C-130J (Hercules) aircraft. For this safety-critical application, the software process requirements were: • a rigorously verified, error-free end product, right first time, • modularity, portability, ease of functional modification and extension of software components, essential for an aircraft with a long life, • rapid, low-cost development. These aims were met by investing in “correctness by construction”: • integration of the US Software Productivity Consortium's CoRE requirements expression method, the graphical Domain-Specific Design Language (DSDL), and multi-level design in Ada to strict rules, enforced by templates and mechanical checks, • use of SPARK Ada, allowing mechanical code verification against CoRE specifications. Large savings in V & V were achieved, through: • reduced cost of testing to DO-178B Level A requirements, and • mechanisation of semantic analysis (as required by MoD).