Composing distributed systems from reusable aspects of behavior

Research on aspect oriented programming and specification has highlighted the need to deal with cross-cutting concerns that involve more than one implementation level component. Distributed systems are an important application area where cross-cutting concerns frequently emerge. We present a novel way of composing distributed behavior from reusable superposition steps. The steps are given in a joint action notation, which allows the introducing of logically related data and operations in several implementation level components simultaneously. A superposition step contains a description of the context in which it is applicable, and the additional structure to add to a specification. Aspects of collective behavior may overlap at the implementation level. To make it possible to separate aspects cleanly at the specification level, our specification method allows entities to be merged in composition to allow an implementation level entity to play multiple specification level roles.