Adding Extra Dimensions to Message Sequence Charts : Visualizing Component and Date Variability

Abstract: Message Sequence Charts (MSC) are now widely used to describe communication between system components. The diagrams have been formalized, recommended, and even extended. The extensions of the MSCs typically handle additional complexities, e.g. expressing multiplicities. Certain MSC instances are substitutable or omissible with no or minimal effect in the drawings. Additionally, system changes over time would be more easily observed, compared, and maintained if they are visualized in one drawing. This thesis introduces a concept of Master Chart to extend the MSCs. It is done as a case study in Scania, a heavy truck and bus manufacturer. Contextual inquiry and PACT framework are employed to generate design ideas. Then a prototype .NET application is developed and compared with an existing MSC drawing tool. All test subjects successfully completed the drawing tasks in the prototype tool albeit more slowly than in the old tool. Usability issues are discussed for future full-scale implementation. Based on this study, having the Master Chart as an extension to traditional MSCs seems to create more meaningful and maintainable drawings especially on systems with a lot of variability.