Summary

Simulation has proven to be a useful technique for validating interaction-centred software engineering notations, most prominently Message Sequence Charts ^[8], especially in the early phases of software development. The “Unified Modeling Language” (UML ^[2]), the emerging standard software development and description language, also comprises a notion of interaction modelling, so-called collaborations, and simultaneously features a sound abstract syntax and a rich and detailed, though informal, semantics for this concept. However, the obvious transfer of known simulation results is limited by some semantical deviations and the integration of new characteristics, since additional influences from OOSE's interactions, OMT's collaborations, and rôle modelling in general have been combined: In an UML model, collaborations specify how an operation or an use case of the model is realised by a cooperation of several instances of model elements. The static aspects of a collaboration are given by a context of class and association rôles describing which features actually participating instances have to show. For the dynamic aspects a collaboration defines an interaction, specifying which actions have to be performed by participating instances, which stimuli to other participating instances these actions have to dispatch, and in which order these stimuli can be sent sequentially or concurrently. The precise semantics of UML collaborations has been elaborated to some extent ^{[7.], [12.], [6.] and [1.]}, but these investigations have not focussed on simulation of a collaboration's behaviour.