Reo is a channel-based exogenous coordination language in which complex coordinators, called connectors, are compositionally built out of simpler ones. Each connector in Reo imposes a specific coordination pattern on the entities (e.g., components) that connect to it. Thus, connectors essentially model the protocol or ‘glue code’ between components. The emphasis in Reo is on connectors and their composition only, not on the entities that connect to, communicate, and cooperate through these connectors.
http://reo.project.cwi.nl/v2/