On the Extensibility of Formal Methods Tools

Modern software systems often have long lifespans over which they must continually evolve to meet new, and sometimes unforeseen, requirements. One way to effectively deal with this is by developing the system as a series of extensions. As requirements change, the system evolves through the addition of new extensions and, potentially, the removal of existing extensions. In order for this kind of development process to thrive, it is necessary that the system have a high level of extensibility. Extensibility is the capability of a system to support the gradual addition of new, unplanned functionalities. This dissertation investigates extensibility of software systems and focuses on a particular class of software: formal methods tools. The approach is broad in scope. Extensibility of systems is addressed in terms of design, analysis and improvement, which are carried out in terms of source code and software architecture. For additional perspective, extensibility is also considered in the context of formal modelling. The work carried out in this dissertation led to the development of various extensions to the Overture tool supporting the Vienna Development Method, including a new proof obligation generator and integration with theorem provers. Additionally, the extensibility of Overture itself was also improved and it now better supports the development and integration of various kinds of extensions. Finally, extensibility techniques have been applied to formal modelling, leading to an extensible architectural style for formal models

Specifying and Composing Non-Functional Requirements in Model-based Development

Non-functional requirements encompass important design concerns such as schedulability, security, and communication constraints. In model-based development they non-locally impact admissible platformmappings and design spaces. In this paper we present a novel and formal approach for specifying non-functional requirements as constraintsystems over the space of models. Our approach, based on structured logic programming, allows interacting requirements to be specified independently from each other and composed together. Correct-by-construction operators eliminate some composition mistakes. Our approach is implemented in our formal modeling tool FORMULA, which can analyze the impacts of interacting non-functional requirements on platform mappings and design spaces