On the Relationship Between UML Sequence Diagrams and State Diagrams

The Automated Software Engineering Group (ASE) at NASA Ames Research Center is a research group investigating state-of-the-art veri cation and program generation technologies. As part of this e ort, the ASE recognize the importance of UML within NASA's software projects (e.g., the Mission Data System at the Jet Propulsion Lab, Pasadena) and are currently developing ways in which ASE technologies could be integrated into the UML design process. One of the main problems experienced on large software projects, such as those within NASA, is that di erent notations are necessary for describing di erent aspects of a software system. Whilst the UML provides a collection of such notations, there is only very limited support for maintaining consistency between the di erent models. This leads to costly software errors as inconsistencies that should have been detected at the requirements phase remain present through code development and are only found during testing, at which point they are orders of magnitude more costly to detect and x. The main aim of the PecSee project, led by Jon Whittle and Johann Schumann, is to develop techniques and tools for maintaining consistency and resolving ambiguities between UML models. The initial investigations have concentrated on examining the relationship between models expressed as class diagrams with OCL constraints, sequence diagrams and state diagrams. An algorithm has been developed that can translate between sequence diagrams and state diagrams, taking into account information present in the class diagrams [7]. Clearly, such translations rely on a well-de ned semantics of the participating notations. As such a semantics is not yet available, the approach has been somewhat pragmatic, but may o er suggestions for future semantics-de ning e orts.