Abstract
Adaptation is an important requirement for mobile applicationsdue to the varying levels of resource availabilitythat characterises mobile environments. However withoutproper control, multiple applications can each adapt independentlyin response to a range of different adaptive stimuli,causing conflicts or suboptimal performance. In thispaper we present a policy driven approach for mobile adaptivesystems that can overcome the aforementioned problems.Our system is based on a policy language derivedfrom the Event Calculus logic programming formalism. Importantcharacteristics of our policy language are the supportfor explicit expressions of time dependencies and thesimple and user friendly syntax.