T h e Semantics of th e OCL Action Cl a use

The proposal for the 2.0 version of the UML's Object Constraint Language provides the modeller of object-oriented systems with a way to ex- press the fact that a signal has been send, or an operation has been called. This type of expression is called an Action Clause. This paper defines the Action Clause based on a model of the values in the semantic domain of UML mod- els. In order to define the semantics of the Action Clause a small kernel of the semantic domain of every UML model needs to be specified. This paper uses a specification of the semantic domain based on local object states. These lo- cal object states includes a 'virtual' input and output queue that may contain signals. The Action Clause is defined using the signals in the in- and output queues.