Systematic Evaluation of (Safety) Assurance Cases

An Assurance Case (AC) documents an argument that supports a claim made about a system. An effective Assurance Case provides adequate belief to stakeholders that the system under consideration adequately embodies specific critical properties, for example safety and security. Comprehensive evaluation of an AC is a necessary step in building this belief. This involves measuring confidence in the assurance case argument, but also includes an overall quality assessment of the AC. This paper describes essential components of a (safety) AC evaluation process using previously defined evaluation criteria. These criteria were classified as applying to either structure or content of the (safety) AC. Two example (safety) ACs are used to demonstrate the approach, and for brevity, we illustrate the examples using purely Goal Structuring Notation (GSN) and in a second example, a GSN-like notation.