We define a subset krtUML of UML which is rich enough to express such modelling entities of UML, used in real-time applications, as active objects, dynamic object creation and destruction, dynamically changing communication topologies, combinations of synchronous and asynchronous communication, and shared memory usage through object attributes. We define a formal interleaving semantics for this kernel language by associating with each model a symbolic transition system . We briefly outline how to compile models of industrial systems making use of generalisation hierarchies, weak and strong aggregation, and hierarchical state-machines into krtUML. The main aim of the paper is to provide an executable semantics for krtUML suitable for the formal verification of temporal model properties with existing model-checking tools.
