Metamodel-driven development of an assurance case notation

The Structured Assurance Case Metamodel (SACM) is a standard specified by the Object Management Group that defines a metamodel for representing structured assurance cases. It is developed to support standardisation and interoperability in assurance case development. Unlike existing frameworks such as GSN and CAE, SACM (2.0) was not equipped with any visual notation that can be used to develop graphical assurance cases. A visual notation can be seen as an alternative representation to the textual form of a modelling language that can support the language's adoption by its users. The SACM concept is specified using a metamodel. We identified that there is a lack of a systematic approach that can be adopted to create a visual notation that considers the metamodel as part of the design process. This thesis proposes an approach that considers a metamodel structure as one of the inputs to developing a visual notation. The proposed approach could be used to develop any notation that is based upon a metamodel.

In this thesis, the application of the proposed approach is demonstrated in the development of the SACM notation. The produced SACM notation is evaluated through empirical studies involving novice and experienced users. The evaluation results shows that experienced users found the resulting SACM notation is more intuitive when compared to an existing notation. It is important to notice that the proposed approach requires many distinct design decisions when applying the approach to produce a notation. Thus, the development of the notation is sensitive to the design decision made by the notation designer that could affect the effectiveness of the resulting notation. Based on the evaluation results, the proposed approach is demonstrated to be helpful in developing a visual notation based on a defined metamodel. Furthermore, the resulting SACM notation is also shown to be useful, and able to be adopted by the practitioners to develop assurance cases. This is indicated by the adoption of the produced notation by an international standard body (Object Management Group); the SACM notation has been published as part of version 2.1 of the SACM standard.