Flexible debugging of behavior models

Model-Driven Engineering shifts the focus from code to models as the primary development artifacts. Therefore, also testing and debugging efforts have to focus on models. Some debuggers for modeling languages already exist but they lack the flexibility to fix errors and verify the correction at runtime. In this paper, we consider how debugging concepts of general-purpose programming languages can be mapped to story diagrams, a behavior modeling language, and what has to be considered in general when implementing debuggers for a modeling language. Then, we present a debugger for story diagrams. In addition to common debugging features, it allows to change the executed model at runtime and to revert the execution to an earlier point, which provides a higher flexibility to the developer. After finding an error in the model, the developer does not need to restart the execution from the beginning, but can go back to a point before the error, fix the error, and continue executing the model.