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 time with higher-order behavioral contracts. Contract monitoring is local to a component, and the component is treated as a black box. Thus it does not disturb the highly decoupled nature of distributed components and allows heterogeneous implementation languages and platforms without modifica- tions to a component’s code. We describe the design, seman- tics and properties of CONSUL (adapter transparency and correct blame), and show that its contracts can capture and enforce precise and useful properties of a variety of off-the- shelf components.