ESCAPE: A Component-Based Policy Framework for Sense and React Applications

Sense-and-react applications are characterised by the fact that actuators are able to react to data collected by sensors and change the monitored environment. With the introduction of nodes sporting actuators, Wireless Sensor Networks (WSNs) are being used for realising such applications. Sensor and actuator nodes are capable of interact locally. As a result, the logic that coordinates the activities of the different nodes towards a common goals has to be embedded in the network itself. In this scenario, the development of applications becomes more complex. In this paper, we present a component-based framework that facilitates the development of sense-and-react applications promoting reuse of code. While applications components are used to implement basic functionalities (sense and reaction) our framework allows the specification of application-domain requirements. Our framework is composed of a Publish/Subscribe Broker, a component-based service layer and a Policy Manager. The broker manages subscriptions information and the service layer provides mechanisms orthogonal to publish/subscribe core (e.g., diffusion protocols, data communication protocols, data encryption, etc.). The novelty of our approach is the introduction of the Policy Manager where policies are enforced. Policies are rules that govern the choices and behaviour of the system. They can be used for specifying which services have to be associated with the broker operations. Moreover, policies can embed rules for coordinating the activities of the different sensors and actuators for reaching the common goals of applications.