Supporting Context Awareness in Highly Dynamic Network Environments

Wolfgang Beer
Institute for System Software

Abstract

The aim of context-aware services and applications is to react flexibly on the environmental state. Traditional services and applications are completely independent from their environment and therefore not able to react on state changes in the environment. The introduction of location-based services, which provide location-specific services to the users, represents the first practical appearance of context-aware services. Location-based services take the location information of the service client and return a location-specific service result.

Context awareness is not limited to the location information, but includes all sorts of information which are relevant to classify the situation of a service client.

This PhD thesis introduces a software framework that supports the collection and processing of generic sensor data, in order to provide the information to services and applications. The open framework architecture of the framework enables the use of different transport protocols to deliver the information. The software architecture also enables the integration of new protocol implementations. As an example transport module a web service standard based module was implemented. The integration of web service standards into the transport layer offers language and platform independent service description and delivery for a multitude of different service clients. With the discovery and lookup mechanism of the framework service clients are able to discover service providers even in ad-hoc networks.

One of the main characteristics of the software framework is the possibility to map sensorial state transitions with specific actions. Interpreted rules, which are defined by the application designer or even by a user, realize the mapping between state transitions and the actions. These rules define how the application reacts on a specific state. Through the interpretation of the rules it is possible to change the rule repository or single rules at run time and to change the application’s behavior dynamically.

To discover possible communication partners, the framework implements a role-based classification mechanism. The role-based mechanism uses the collection of a service provider’s service interfaces to decide in which role the service provider acts in an application. Comparable software frameworks often use static classification hierarchies to classify communication partners which leads to problems in ad-hoc networks. The framework enables the creation of context-sensitive applications through XML configurations. XML configurations simplify the use of visual development tools for designing context-sensitive applications.

To demonstrate the framework, four example applications were developed and tested in practice.

PhD thesis. Johannes Kepler University of Linz, 2004