Formal Requirements Modeling for Reactive Systems with Coloured Petri Nets

This dissertation presents the contributions of seven publications all concerned with the application of Coloured Petri Nets (CPN) to requirements modeling for reactive systems. The publications are introduced along with relevant background material and related work, and their contributions to addressing a collection of generic challenges for requirements modeling are discussed. Firstly, two approaches to constructing CPN requirements models based on collections of Use Cases are presented. In both cases, scenarios for the Use Cases are described in terms of UML 2.0 high-level Sequence Diagrams (SDs). The first approach translates collections of Use Cases and their scenarios into executable and hierarchical CPN requirements models. The models are explicitly partitioned in order to make it possible to distinguish the representation of the reactive system from that of its environment. This is important because it represents the identification of what is being designed (the reactive system), and what is given and being made assumptions about (the environment). The representation of the environment is further partitioned to distinguish human actors from non-human actors. This allows the modeler to take into concern that the behavior of human actors is less likely to be predictable than the behavior of e.g. mechanical components. In the second approach, the CPN model is parameterized and utilizes a generic and reusable CPN module operating as an SD interpreter. In addition to distinguishing between system and environment as in the first approach, the CPN model is structured in a way that allows for explicit distinction between requirements and specifications. Assumptions about the behavior of physical entities in the environment are represented as separate CPN modules. Next, an approach to addressing the problem of validating formal requirements models through interactive graphical animations is presented. Executable Use Cases (EUCs) provide a framework for integrating three tiers of descriptions of specifications and environment assumptions: the lower tier is an informal description, the middle tier is a CPN model representing the contents of the lower tier, and the upper tier is a domain-specific graphical and interactive animation driven by the CPN model. It allows stakeholders to validate the formal requirements model by interacting and experimenting with it through a graphical interface composed of recognizable artifacts and activities. The presentation of the three publications related to Use Cases is followed by a the presentation of a publication formalizing some of the guidelines applied for structuring the CPN requirements models — namely the guidelines that make it possible to distinguish the modeling artifacts describing the environment from