The HEAT/ACT Preliminary Safety Case: A case study in the use of Goal Structuring Notation

Chinneck, P., Pumfrey, D. and McDermid, J.

    The HEAT/ACT project consists of replacing the conventional mechanical flight control system of a helicopter with a fly-by-wire system. With such a project, the safety concerns are obvious, and therefore the development of a thorough and convincing Safety Case is paramount. The project therefore chose to adopt a phased approach to safety case development, beginning with a Preliminary Safety Case (PSC). Goal Structuring Notation (GSN) was chosen as the development method for the PSC, because of its perceived merits of ease of construction and clarity of review. This work was first reported in a presentation at the UK Safety Critical Systems Symposium (SSS'04), which described the initial development of the PSC argument structure, and investigated some of the practical issues identified in using GSN. This paper revisits the HEAT/ACT project. It reprises the original construction of the GSN argument, and goes on to show how the PSC has developed and evolved since that initial development phase. It examines how the GSN argument has been used in the interaction with other partners and sub-system suppliers involved in the HEAT/ACT project, and considers whether the effort expended in developing the PSC has lived up to expectations in its contribution to safety process management.
Cite as: Chinneck, P., Pumfrey, D. and McDermid, J. (2004). The HEAT/ACT Preliminary Safety Case: A case study in the use of Goal Structuring Notation. In Proc. Ninth Australian Workshop on Safety-Related Programmable Systems (SCS 2004), Brisbane, Australia. CRPIT, 47. Cant, T., Ed. ACS. 33-41.
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