A trace-based semantics for responsiveness

In the context of asynchronously communicating services, responsiveness guarantees that a service and its environment have always the possibility to communicate. The responsiveness preorder describes when one service can be replaced by another such that responsiveness is preserved. We study responsiveness for possibly unbounded services with and without final states, and present for both preorder variants a semantical characterization based on traces. Surprisingly, the preorders turn out not to be precongruences, and for both we characterize the coarsest precongruence which is contained in the respective preorder