Interaction Patterns for Communicating Processes

Interaction dynamics describe the way entities relate and communicate with one another. Just as people interact in a variety of ways, communicating processes, such as software components, can also interact in many and highly complex ways. The software world is filled with examples of systems utilizing processes, objects, components, device drivers and entities by other names -interconnected in different ways and with different purposes. But in the seeming chaos there is order. Interactions between communicating entities have many basic properties which can be isolated, described and used across many application domains and in many situations. This paper identifies some fundamental patterns that apply to communicating processes in general and software components in particular. The patterns can be used alone or in combinations, allowing more complex patterns to be built out of simpler ones. The success of components as a software technology is predicated on reuse and ease of reuse. In software component terms, ease of reuse is determined by how easily components can be interconnected, which depends solely on their interfaces and the interactions supported by those interfaces. By recognizing the existence of standard interaction patterns, and applying them to interfaces, components should be easier to interconnect, and therefore reuse.