Defining metrics for UML statechart diagrams in a methodological way

The fact that the usage of metrics at early phases of 00 development can help designers make better decisions is gaining relevance. Moreover, the necessity of having early indicators of external quality attributes, such as understandability, based on early metrics is growing. There exists several works related to metrics for UML structural diagrams such as class diagrams. However, UML behavioral diagrams metrics have been disregarded in the software measurement arena. This fact leaded us to define a set of metrics for the size and structural complexity of UML statechart diagrams. Apart from the definition of the metrics, a contribution of this study is the methodological approach that was followed to theoretically validate them and to empirically validate them as understandability indicators.