Higher-order Behavioral Contracts for Distributed Components

Inspired by the Design by Contract paradigm, we intro-duce CONSUL, a contract system for distributed compo-nents. CONSUL monitors distributed components at run timewith higher-order behavioral contracts. Contract monitoringis local to a component, and the component is treated asa black box. Thus it does not disturb the highly decouplednature of distributed components and allows heterogeneousimplementation languages and platforms without modifica-tions to a component’s code. We describe the design, seman-tics and properties of CONSUL (adapter transparency andcorrect blame), and show that its contracts can capture andenforce precise and useful properties of a variety of off-the-shelf components.