User-Centric Web Services for Ubiquitous Computing

Abstract

One of the key issues in ubiquitous computing environments is to realize user centricity, which is about enabling Web-based services and services in general to be prepared, supported and delivered from the perspective of users rather than system elements. To accomplish user centricity, it is essential to deal with the high-level goals of multiple users and with dynamic changes of contextual information. The approach of task-oriented computing is a means of realizing a user-centric service provision in Ubiquitous Computing environments. This approach represents users’ goals in tasks, which are then bound to available service instances. This chapter describes the essential requirements for a user-centric service provision in Ubiquitous Computing environments. User centricity, context awareness, composability and dynamicity are such requirements. Existing works regarding service provision in Ubiquitous Computing are analyzed by highlighting their limitations in the light of those requirements. This chapter also describes a service framework for Ubiquitous Computing. This framework consists of three layers - the task layer, the composition-pattern layer and the service layer. The essential semantic elements that describe a task are arranged in a task description model. That model is used by a semantically based mechanism to select appropriate tasks based on context information. It is also utilized by a pattern-based service composition mechanism. The framework is illustrated by a demo application example developed in our test bed. By leveraging the task-oriented computing approach, this chapter contributes to enhancing the reusability of tasks and patterns, improving flexibility when developing Ubiquitous Computing applications and providing dynamism to the service provision in this type of environments.