Coordinated Adaptation for Adaptive Context-aware Applications

The ability to adapt to change is critical to both mobile and context-aware applications.

This thesis argues that providing suf?cient support for adaptive context-aware applications

requires support for coordinated adaptation. Speci?cally, the main argument

of this thesis is that coordinated adaptation requires applications to delegate adaptation

control to an entity that can receive state information from multiple applications and

trigger adaptation in multiple applications. Furthermore, coordination requires support

for recon?guration of the adaptive behaviour and user involvement. Failure to support

coordinated adaptation is shown to lead to poor system and application performance and

insuf?cient support for user requirements.

An investigation of the existing state-of-the-art in the areas of adaptive and contextaware

systems and an analysis of the limitations of existing systems leads to the establishment

of a set of design requirements for the support of coordinated adaptation.

Speci?cally, adaptation control should be decoupled from the mechanisms implementing

the adaptive behaviour of the applications, applications should externalise both state

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information and the adaptive mechanisms they support and the adaptation control mechanism

should allow modi?cations without the need for re-implementation of either the

application or the support platform.

This thesis presents the design of a platform derived from the aforementioned requirements.

This platform utilises a policy based mechanism for controlling adaptation.

Based on the particular requirements of adaptive context-aware applications a new policy

language is de?ned derived from Kowalsky's Event Calculus logic programming

formalism. This policy language allows the speci?cation of policy rules where conditions

are de?ned through the expression of temporal relationships between events and

entities that represent duration (i.e. ?uents). A prototype implementation of this design

allowed the evaluation of the features offered by this platform. This evaluation reveals

that the platform can support coordinated adaptation with acceptable performance cost.