The UML is an influential and widespread notation for high-level modelling of information processing systems. UML statechart diagrams are a graphical language to describe system behaviour. They consitute one of the most intensively-used formalisms comprised by the UML. However, statechart diagrams are lacking concepts for describing real-time, performance, dependability and quality of service (QoS) characteristics at a behavioural level.This note describes a QoS-oriented extension of UML statechart diagrams, called StoCharts. StoCharts enhance the basic statechart formalism with two distinguished features, both simple and easy to understand, yet powerful enough to model a sufficiently rich class of stochastic processes. This is illustrated by a selection of case studies performed using StoCharts. We review the main ingredients of StoCharts and survey tool support and case studies performed with the language, and place StoCharts in the context of other extensions of statechart diagrams.
Jansen, D. N., Hermanns, H., Haverkort, B. R. H. M. (Ed.), & Katoen, J. P. (2005). QoS modelling and analysis with UML-statecharts: the StoCharts approach. Performance Evaluation Review, 32(4), 28-33. https://doi.org/10.1145/1059816.1059822