Currently, I am working with Ha Nguyen on the manipulation of protocols using VPA-based aspects  whose pointcut language is of expressiveness strictly larger than finite-state protocols but strictly smaller than context-free languages.
Previously, in the context of a component-model with explicit finite-state protocols, I have worked on composition properties and the construction of component applications using protocol composition operators . Recently, we have extended this model by integrating it with a notion of aspects (in the sense of AOP) and investigated the application of this augmented model to dependency concerns .
Furthermore, I have considered non-regular protocols for component interfaces  and their application to availability properties.
 H. Nguyen, M. Südholt: "VPA-based aspects: better support for AOP over protocols", 4th IEEE International Conference on Software Engineering and Formal Methods (SEFM'06), Sep. 2006.
 A. Farías, M. Südholt: "On components with explicit protocols satisfying a notion of correctness by construction", DOA'02, Oct. 2002.
 A. Farías, M. Südholt: "Integrating protocol aspects with software components to address dependability concerns", TR 04/6/INFO, École des Mines de Nantes, Nov. 2004.
 M. Südholt: "A model of components with non-regular protocols", 4th Int. WS on Software Composition at ETAPS (SC'05), LNCS, Springer Verlag, April 2005.