Foundations for Ensemble Modeling - The Helena Approach - Handling Massively Distributed Systems with ELaborate ENsemble Architectures

Ensembles are groups of active entities that collaborate to perform a certain task. Modeling software systems for ensemble execution is challenging since such applications are highly dynamic involving complex interaction structures of concurrently running individuals. In this work, we propose a formal foundation for ensemble modeling based on a rigorous semantic framework. Our approach is centered around the notion of a role expressing the capabilities that a component needs when participating in a speci c ensemble. We use ensemble structures to model the structural aspects of collaborations and labeled transition systems to specify the dynamic behavior typical for performing a certain role. Our approach is driven by a clear discrimination between types, used on the speci cation level, and instances, which form concrete ensembles in an ensemble automaton. The semantics of an ensemble speci cation is given by the class of all ensemble automata which adhere to the properties of an ensemble structure such that any ensemble member, playing a certain role, exhibits a behavior that is allowed by the role behavior speci cation.