Research And Implementation Of Context Information Server In Pervasive Computing

With the development of computer technology, wireless network and embedded system, the traditional computing pattern can no longer meet the needs of people who desires for enjoying the existing computing power and information services anytime, anywhere, transparently and conveniently. The goal of pervasive computing is to make people's position into master of computer from "servant" and allow users to focus their attention on their tasks.Context-aware computing is a critical technology which implements "people-oriented". By taking advantage of context information, context-aware computing makes applications "know" the current environment and the changes that had occurred, and then take appropriate strategies to change some of their behavior to supply users for information services considerately. However, pervasive environment is an open environment with much complex context information. How to make use of context to supply context services is an important researching field of context-aware computing and is of important theoretic significance and practical value.Because of size and mobility, pervasive devices have very limited computing power in pervasive environment. Placing public services that require running on powerful hardware on high performance computing devices is necessary. Based on the deeply researching on classical context-aware computing models, such as Context Toolkit, and analysis of their characteristics and flaws, this thesis studied and established a Context Information Service Server (CISS) model and implemented the CISS model.CISS model is composed of four main components, context manager, context reasoner, context querier and event manager. This model adopts OWL to describe context ontology and standard structured SPARQL RDF query language to query context. At last, this model uses inference mechanism about context based on OWL and customized rules to detect consistency or confliction. Besides, the event triggering mechanism is built to supply event services for context-aware application system. Instructed by the thinking of layering design, AOP and SOA, CISS system basically implemented context manager, context reasoning, context query services and context event services.Through CISS server, context-aware applications can share in context resources and sensors. Meanwhile, coupling between various modules is reduced effectively, so that developers can concentrate on their own tasks. As a result, the complexity of system development decrease and the efficiency of context-aware application development improve.