Structural changes, i.e. the creation and deletion of components, and the change of interactions are salient features of adaptive systems. To model and specify these systems variable structure models are required, i.e. models that entail in their own description the possibility to change their structure. To execute these models a simulator with a clear semantic of intertwining structural and non-structural changes is required.

In JAMES different simulator components, e.g. for paced, unpaced, sequential, and parallel simulation, support the continuous use of models and simulation from specification to testing and a composition of the simulation engine on demand. Two types of simulator components for variable structure models are developed, integrated into the simulation layer, and the implications discussed.