Friday, Adrian (1996) Infrastructure support for adaptive mobile applications. PhD thesis, Lancaster University.
Abstract
Recent growth in the number and quality of wireless network technologies has led to an increased interest in mobile computing. Furthermore, these technologies have now advanced sufficiently to allow 'advanced applications' to be engineered. Applications such as these are characterised by complex patterns of distribution and interaction, support for collaboration and multimedia data, and are typically required to operate over heterogeneous networks and end-systems. Given these operating requirements, it is the author's contention that advanced applications must adapt their behaviour in response to changes in their environment in order to operate effectively. Such applications are termed adaptive applications. This thesis investigates the support required by advanced applications to facilitate operation in heterogeneous networked environments. A set of generic techniques are presented that enable existing distributed systems platforms to provide support for adaptive applications. These techniques are based on the provision of a QoS framework and a supporting infrastructure comprising a new remote procedure call package and supporting services. The QoS framework centres on the ability to establish explicit bindings between objects. Explicit bindings enable application requirements to be specified and provide a handle through which they can exert control and, more significantly, be informed of violations in the requested QoS. These QoS violations enable the applications to discover changes in their underlying environment and offer them the opportunity to adapt. The proposed architecture is validated through an implementation of the framework based on an existing distributed systems platform. The resulting architecture is used to underpin a novel collaborative mobile application aimed at supporting field workers within the utilities industry. The application in turn is used as a measure to gauge the effectiveness of the support provided by the platform. In addition, the design, implementation and evaluation of the application is used throughout the thesis to illustrate various aspects of platform support.