Scenario-based specifications have a wide acceptance in industry as approximations of intended behavior. Their use is mainly informal, with no precise semantics associated with the scenario description. On the other hand, industry has been slow in assimilating behavioral modeling and verification technologies. Nevertheless, they boast an important mathematical foundation: effective tools for behavioral analysis.
This paper proposes the use of scenarios and behavior models complementarily, as alternative views of how system components interact. The main contribution of this work is a process for incremental behavior elaboration. The proposed process supports elaboration of behavior models in conjunction with scenarios. The authors propose driving such elaboration using the concept of implied scenarios.
Implied scenarios expose subtle mismatches between the architecture and behavior. These gaps do not necessarily mean incorrect behavior. An implied scenario may simply mean that an acceptable scenario has been overlooked, and that the scenario specification needs to be completed. Alternatively, the implied scenario may represent unacceptable behavior. The decision of whether to accept or reject an implied scenario depends on the problem domain, and should be validated by stakeholders. Implied scenarios force stakeholders to address subtle, yet crucial points regarding the system they are specifying.
The authors propose an artifact that supports the detection of implied scenarios, by comparing their traces against those of the minimal architecture model. Since mismatches between the scenario-based specification and the architecture cannot be detected trivially, by observing the specification, there is great value in automatically detecting and validating implied scenarios.
The paper is well written, and the explanations are illustrated by a toy example that is used throughout the paper to help understanding. Although there are a lot of formal definitions, they are also explained informally, which makes reading the paper easier.
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