Chapter

Computer Safety, Reliability, and Security

Volume 8153 of the series Lecture Notes in Computer Science pp 21-32

A Formal Basis for Safety Case Patterns

  • Ewen DenneyAffiliated withLancaster UniversitySGT / NASA Ames Research Center
  • , Ganesh PaiAffiliated withLancaster UniversitySGT / NASA Ames Research Center

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Abstract

By capturing common structures of successful arguments, safety case patterns provide an approach for reusing strategies for reasoning about safety. In the current state of the practice, patterns exist as descriptive specifications with informal semantics, which not only offer little opportunity for more sophisticated usage such as automated instantiation, composition and manipulation, but also impede standardization efforts and tool interoperability. To address these concerns, this paper gives (i) a formal definition for safety case patterns, clarifying both restrictions on the usage of multiplicity and well-founded recursion in structural abstraction, (ii) formal semantics to patterns, and (iii) a generic data model and algorithm for pattern instantiation. We illustrate our contributions by application to a new pattern, the requirements breakdown pattern, which builds upon our previous work.

Keywords

Safety cases Safety case patterns Formal methods Automation