Formalisation of SysML Models and Analysis based on Refinement

The increasing complexity of systems has led to increasing difficulty in design. For critical systems, for which safety is a major concern, early verification and validation (V&V) is recognised as a valuable approach to promote dependability. We address these issues with a refinement technique for SysML supported by tools. In this work we describe our semantics for SysML, which is defined using a state-rich process algebra called CML and implemented in a tool for automatic generation of formal models. We also show how the semantics can be used for refinement-based analysis and development. Our case studies are a leadership-election protocol, a critical component of an industrial application, and a dwarf signal, a device used to control rail traffic. Our contributions are: a set of guidelines that provide meaning to the different modelling elements of SysML used during the design of systems; the individual formal semantics for SysML activities, blocks and interactions; an integrated semantics that combines these semantics with another defined for state machines; and a framework for reasoning using refinement about systems specified by collections of SysML diagrams.