An OCL Extension for Real-Time Constraints

The Object Constraint Language (OCL) was introduced to support the specification of constraints for UML diagrams and is mainly used to formulate invariants and operation preand postconditions. Though OCL is also applied in behavioral diagrams, e.g., as guards for state transitions, it is currently not possible to specify constraints concerning the dynamic behavior and timing properties of such diagrams. This article discusses OCL’s application for the dynamic behavior of UML Statechart diagrams and presents an OCL extension for specification of state-oriented time-bounded constraints. We introduce operations to extract state configurations from diagrams and define additional predicates over states and state configurations. The semantics of our OCL extension is given by employing time-bounded Computational Tree Logic (CTL) formulae. An example of a flexible manufacturing system with automated guided vehicles demonstrates the application of our extension.