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Incremental Elaboration of Scenario-Based Specifications and Behavior Models Using Implied Scenarios. Sebastian Uchitel, Jeff Kramer, Jeff Magee Department of Computing, Imperial College. Behavior Model
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Incremental Elaboration of Scenario-Based Specifications and Behavior Models Using Implied Scenarios Sebastian Uchitel, Jeff Kramer, Jeff Magee Department of Computing, Imperial College
Behavior Model Precise, abstract description of the intended behavior of a system that can be used to support rigorous analysis and mechanical verification of properties.
Scenario-based Specifications Such as message sequence charts (MSCs) and UML sequence diagrams are popular as part of requirements specification. Scenarios describe how system components, the environment and users work concurrently and interact.
Implied Scenarios The concept that drives the elaboration process is that of implied scenarios. Implied scenarios identify gaps in scenario-based specifications that arise from specifying the global behavior of a system that will be implemented component-wise.
Elaboration Process Starts with a MSC specification that includes basic and negative MSCs. Implied scenario detection is performed by synthesis and automated analysis of behavior models.
Case Study This case study is presented from a stakeholders point of view, with implied scenarios that must be accepted or rejected. The setting is that of the development of a transport system. Initially, we know only that it consists of high-speed vehicles that transport one person at a time. Passengers can only embark at terminals where they select the destination terminal.
The elaboration process resulted in several aspects of the system that were not expressed in the first version of the MSC specification. After 12 iterations, the MSC specification has no more implied scenarios to be validated. Starting from two very simple scenarios, by detecting implied scenarios we have extended the specification to a total of seven MSCs and eight negative scenarios.
Conclusion In principle, the elaboration process cannot be guaranteed to converge to a stable specification where there are no more implied scenarios. This is reasonable as, on each acceptance of an implied scenario, stakeholders could keep on introducing new functionality in the form of traces that the underlying architecture model could not perform.