Analysing Dependability Case Arguments Using Quality Models
The Goal Structuring Notation (GSN) facilitates a clear presentation of the argument structure in dependability cases for dependable systems. However, assessment of an argument structure with respect to validity, sufficiency and consistency of argumentation and the provided evidence still strongly depends on individual, tacit expert knowledge. We propose a 2-phase analysis method for argument structures:
Firstly, syntactic completeness, consistency, and proper instantiation of argument patterns are examined using a UML profile for GSN and OCL constraints. For the second phase, we propose 2-dimensional quality models to assist the expert in explicitly judging on the conclusiveness of argumentation. A quality model explicitly represents the impact of facts on design activities and software-system’s properties relevant for dependability. The impact value aggregates state-of-the-art knowledge and standard’s recommendations. Missing, negative or conflicting impact indicates impairment of the argument either by revealing a gap in the line of arguments or incompatibilities or opposing principles between decisions or techniques in the process. We show first steps towards the integration of the analysis into model-based tool supported development.
KeywordsSafety Case Dependability Case Argument structures Argument Assessment Quality models Model-based development
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