The potential of the action-oriented paradigm has been explored in the development of a specification language, DisCo, which can be characterized as both action-oriented and object-oriented. Its possibilities are introduced by contrasting them to the more familiar process-oriented approaches. Its execution model is state-based and leads to direct application of temporal logic in formal reasoning. Action-orientation allows a natural support for such forms of modularity that cut across process boundaries. At the same time, process-oriented abstractions are retained by object-orientation and the use of hierarchical state chart structures. The novel aspects of modularity are illustrated by a protocol example. The language is semi-executable.>