Formalizing Propagation of Priorities in Reo, Using Eight Colors

Reo is a language for programming of coordination protocols among concurrent processes. Central to Reo are connectors: programmable synchronization/communication mediums used by processes to exchange data. Every connector runs at a clock; at every tick, it enacts an enabled synchronization/communication among processes. Connectors may prioritize certain synchronizations/communications over others. “Passive” connectors use their priorities only at clock ticks, to decide which enabled synchronization/communication to enact. “Active” connectors, in contrast, use their priorities also between clock ticks, to influence which synchronizations/communications become enabled; they are said to “propagate their priorities”. This paper addresses the problem of formalizing propagation of priorities in Reo. Specifically, this paper presents a new instantiation of the connector coloring framework, using eight colors. The resulting formalization of propagation of priorities is evaluated by proving several desirable behavioral equalities.