Semantics of Concurrent Processes: Unification and New Directions

During the last years, we have developed a multiparadigm unified framework to present all the semantics in the Van Glabbeek's linear time-branching time spectrum and others, in such a way that we can easily appreciate the similarities and differences between them, and also develop generic proofs that are valid for all the semantics satisfying certain hypothesis. Based on the very natural concept of constrained simulation, we show how we can classify the semantics in layers and how to obtain in a generic way the equational, observational and logical characterizations of the semantics in each layer. We have shown the flexibility of our approach by also studying some new semantics, where certain actions have a contravariant character, seeing how to change the characterizations of the semantics when covariant and contravariant actions have to be considered together.