Distributed Context Monitoring for the Adaptation of Continuous Services

This paper describes a middleware designed for distributed context acquisition and reconciliation intended to support the adaptation of continuous Internet services, like e.g., multimedia streaming. These services persist in time, and are characterized by multiple transmissions of data by the service provider, as a result of a single request from the user. Adapting these services to the current context requires the continuous monitoring of context data, and a real-time adjustment of the adaptation parameters upon the detection of a relevant context change. The proposed solution is based on asynchronous context change notifications, and specific techniques have been designed to minimize the number of unnecessary updates and the re-evaluation of policies. The paper also provides experimental results obtained by developing an adaptive video streaming system and running it on top of the proposed middleware.