| Mobile computing represents a shift in the distributed systems paradigm. The potential of decoupled and disconnected operation, location-dependent computation and communication, and powerful portable computing devices gives rise to opportunities for new patterns of distributed computation that require a revised view of distributed systems. However, factors such as weak network connectivity, energy constraints, and mobility itself raise new concerns regarding the security, reliability, and even correctness; of a mobile computing system.;In this dissertation, we complement recent research in mobile computing by addressing the problem from the viewpoint of building a mobile computing application. It is our hypothesis that a mobile computing application must be made aware of mobility not only to better utilize constrained resources, but also to provide enhanced mobility related functionality. Towards this end, the application must adapt in response to the changing mobile environment. Unfortunately, the wide variety of environmental situations that mobile computing presents makes it difficult to build an application that optimally handles all situations. This makes it imperative to consider structuring alternatives for both mobile computing applications, and the underlying run-time system on which they depend.;We first consider the problem of exposing an application to the effects of mobility. We present a novel architecture for managing and reporting changes in the mobile environment to an application. In this architecture, an environmental change is modeled as an asynchronous event that can be handled at the level of abstraction that an application deems appropriate. Our prototype implementation serves as a reference, documenting the issues that must be considered when designing the underlying run-time for adaptive mobile computing applications.;Second, we propose an application architecture that balances the trade-off between hiding and exposing mobility awareness. Basic application functionality in this architecture, is cleanly decoupled from adaptiveness, allowing the application to evolve independently of any particular environmental situation. We describe our experience in realizing this architecture, and conclude that it forms a powerful basis not only for building new mobility aware applications, but also to incorporate mobility aware adaptiveness into legacy applications and middle-ware. |
