Model based system assurance using the structured assurance case metamodel

Abstract

Assurance cases are used to demonstrate confidence in system properties of interest (e.g. safety and/or security). A number of system assurance approaches are adopted by industries in the safety-critical domain. However, the task of constructing assurance cases remains a manual, trivial and informal process. The Structured Assurance Case Metamodel (SACM) is a standard specified by the Object Management Group (OMG). SACM provides a richer set of features than existing system assurance languages/approaches. SACM provides a foundation for model-based system assurance, which has great potentials in growing technology domains such as Open Adaptive Systems. However, the intended usage of SACM has not been sufficiently explained. In addition, there has been no support to interoperate between existing assurance case (models) and SACM models.In this article, we explain the intended usage of SACM based on our involvement in the OMG specification process of SACM. In addition, to promote a model-based approach, we provide SACM compliant metamodels for existing system assurance approaches (the Goal Structuring Notation and Claims-Arguments-Evidence), and the transformations from these models to SACM. We also briefly discuss the tool support for model-based system assurance which helps practitioners to make the transition from existing system assurance approaches to model-based system assurance using SACM.

New Opportunities for Integrated Formal Methods

“…Consequently, there have been a number of efforts to formalise and mechanise assurance cases, both at the argumentation level [37,161] and the evidence level [32]. More recently, in MDE, the Structured Assurance Case Meta-model (SACM) 9 is a standardised meta-model that supports both structured argumentation and integration of evidence from diverse system models [172]. SACM unifies several existing argumentation notations, and also provides support for artefact traceability and terminology.…”

“…The authors highlight the use of what are called integrated formal methods (iFMs) 3 in the construction of assurance cases and the production of evidence as a key opportunity to meet current RAS challenges. Particularly, computer-assisted assurance techniques [172], supported by evidence provided by iFMs, can greatly increase confidence in the sufficiency of assurance cases, and also aid in their maintenance and evolution through automation. Moreover, the use of modern FMbased tools to support holistic simulation, prototyping, and verification activities, at each stage of system, hardware, and software development, can lead to systems that are demonstrably safe, secure, and trustworthy.…”

Isabelle/SACM: Computer-Assisted Assurance Cases with Integrated Formal Methods

“…Assurance cases (ACs) are structured arguments, supported by evidence, intended to demonstrate that a system meets its requirements, such as safety or security, when applied in a particular operational context [24,30]. They are recommended by several international standards, such as ISO26262 for automotive applications.…”

“…An AC consists of a hierarchical decomposition of claims, through appropriate argumentation strategies, into further claims, and eventually supporting evidence. Several AC languages exist, including the Goal Structuring Notation (GSN) [24], Claims, Arguments, and Evidence (CAE) [2], and the Structured Assurance Case Metamodel (SACM) 1 [30], a standard that unifies several notations.…”

“…AC creation can be supported by model-based design, which utilises architectural and behavioural models over which requirements can be formulated [30]. However, ACs can suffer from logical fallacies and inadequate evidence [20].…”