Operational analysis of sequence diagram specifications

This thesis is concerned with operational analysis of UML 2.x sequence diagram specifications. By operational analysis we mean analysis based on a characterization of the executions of sequence diagrams, or in other words an operational semantics for sequence diagrams. We define two methods for analysis of sequence diagram specifications – refinement verification and refinement testing – and both are implemented in an analysis tool we have named ‘Escalator’. Further, we make the first steps in the direction of extending our approach with support for availability analysis. In order to facilitate operational analysis, we define an operational semantics for UML 2.x sequence diagrams. The operational semantics is loyal to the intended semantics of UML, and is proven to be sound and complete with respect to the denotational semantics for sequence diagrams defined in STAIRS – a framework for stepwise development based on refinement of sequence diagram specifications. The operational semantics has a formalized meta-level, on which we define execution strategies. This meta-level allows us to make distinctions between positive and negative behavior, between potential and universal behavior, and between potential and mandatory choice, all of which are inherently difficult in an operational semantics. Based on the operational semantics and its formalized meta-level, we define trace generation, test generation and test execution. Further, based on a formalization of refinement in STAIRS, the trace generation is used to devise a method for refinement verification, and the test generation and the test execution are used to define a method for refinement testing. Both are methods for investigating whether or not a sequence diagram specification is a correct refinement of another sequence diagram specification. The operational semantics, the refinement verification and the refinement testing are implemented with the term rewriting language Maude, and these implementations are integrated in the Escalator tool. In addition, Escalator provides a graphical user interface for working with sequence diagram specifications and for running the analyses. In order to facilitate availability analysis, we define a conceptual model for service availability where the basic properties of availability are identified. Further, we extend the operational semantics with support for one class of these basic properties, namely real-time properties, and outline how the operation semantics extended with time can be applied to make methods for timed analysis of sequence diagram specifications.