Sophia: An information plane for networked systems

This paper motivates and describes an example network Information Plane, called Sophia, currently deployed on PlanetLab. Sophia is a distributed system that collects, stores, propagates, aggregates, and reacts to observations about the network's current conditions. Sophia's approach is novel: it can be viewed as a multi-user distributed expression evaluator in which sensors and actuators form the ground terms, and statements take on the complete expressiveness of a logic language like Prolog. This paper argues that this approach has several advantages in managing and controlling a complex, federated, and evolving network: (1) a declarative logic language provides a natural way to express the kinds of statements that are common to this application domain, through temporal and positional logic rules, facts and expressions; and (2) distributed evaluation of such logic expressions provides many opportunities for performance optimization yielding an efficient system.