Formal modeling of space shuttle software change requests using SCR

This paper describes a feasibility study into the use of a formal requirements modeling method (SCR) to assist with independent verification and validation of change requests for space shuttle flight software. The goal of the study was to determine whether a formal modeling technique could automate some of the manual analysis tasks performed on change requests, including consistency checking. To analyze the change request, the key part of the original functionality was modeled in SCR. The model was then updated to reflect the proposed changes. Tool support was used to perform consistency checking and to validate the model against domain properties. The study showed that as an analysis tool, formal modeling offers some advantages over inspection-based approaches. However, the problem of analyzing change requests is sufficiently different from other requirements modeling tasks that some specialist tools will be needed. The paper ends with a discussion of the demands of these needs.