Coordination through Channel Composition

Abstract

Ρ_εω is a channel-based exogenous coordination model wherein complex coordinators, called connectors are compositionally built out of simpler ones. The simplest connectors in Ρ_εω are a set of channels with well-defined behavior supplied by users. Ρ_εω can be used as a language for coordination of concurrent processes, or as a “glue language” for compositional construction of connectors that orchestrate component instances in a component-based system. The emphasis in Ρ_εω is on connectors and their composition only, not on the entities that connect to, communicate, and cooperate through these connectors. Each connector in Ρ_εω imposes a specific coordination pattern on the entities (e.g., components) that perform I/O operations through that connector, without the knowledge of those entities.

Channel composition in Ρ _εω is a very powerful mechanism for construction of connectors. In this paper, we demonstrate the expressive power of connector composition in Ρ _εω through a number of examples. We show that exogenous coordination patterns that can be expressed as (metalevel) regular expressions over I/O operations can be composed in Ρ _εω out of a small set of only five primitive channel types.