Research On Key Techniques Of Component-based Middleware For Pervasive Computing

Pervasive computing aims at establishing human-centered calculating environment at the basis of calculation and communication exist at anyplace. Since the concept of pervasive computing was proposed at 1991, more and more people began to pay attention to this new-style computing mode, which is considered a reform of the way people use computing and information. Pervasive computing covers fields of architecture, middleware, mobile computing, human-computer interaction, embedded technology, sensing device, network technique, etc. At present, pervasive computing architecture studies focus on high level concept model which contains the equipment, middleware, and human-computer interaction. As the core between equipment and application, the research of middleware become hotspot.The Pervasive computing middleware features in mobility, distributivity, self-adaptability, heterogeneity, interoperability and expansibility. The better way to actualize these characters is to use micro-kernel framework of component-based combined with service-oriented approach. Featuring in light weight, function adjustable and easy expansibility, the component-based micro-kernel framework can be extracted into a minimal middleware core and a number of expansion modules, so that it can be dynamically registered at runtime, uninstall components, in order to adapt to the dynamic changes of the environment. Through defining the specifications of the component interface to expand and develop new components, the micro-kernel can adapt to the evolution of the application.At first, This thesis studied the theory of pervasive computing middleware. Through the development of pervasive computing and the environmental requirement, to sum up a challenge to middleware technology in software from pervasive computing environment, and study on the major implementation techniques of currently pervasive computing middleware. Through the study found that the current realization technology of pervasive computing middleware, whether it is service-oriented or reflection, are component-based. And component-based technology achieve lightweight and module dynamic loading by means of micro-kernel approach. Along with the further study on pervasive computing, the middleware is necessary integrate component-based and service-oriented features, in order to provide better and improved expansibility for satisfying various demands of pervasive computing environment. Therefore, this thesis on the software component theory and service-oriented OSGi framework for a more in-depth research. Three main contents of software component technique include component model, component interface and component packaging are on discussion, the framework and service of OSGi involved.Then the thesis put forward a lightweight component model-MACAO, a micro-kernel component model, which provides loading and unloading of components, component analysis and implementation as well as the component manager functions. The component model has the following characteristics: ability to express complete components, simple, easy realized, light weight, easy deployed, easy for component packing, well expansibility and configurability, consistency and completeness. Of course, component model rely on the support of computer language, architecture description language-mADL is used to describe the component model which based on XML grammar. mADL describes the minimum set of MACAO model, through the expansion of its grammar structure to achieve expansion of the architecture description, so it has good definability and augmentability. mADL also describes the component information, context information, connector information and deployment information of MACAO component model and make it easy to understand and use. Meanwhile, it is regardless of implementation language, suitable for any programming language to accomplish component model. Applying package way based on active connector to finish the component composition, it controls component interaction via objects outside the component, encapsulates the control and communication which independent of the component, reduces the coupling between components. On the base of the composition way, the concepts of basic component, logic component, node and parameter context are used. Node plays the role of the connector, through the node, connecting basic components to be assembled into a logic component, it can also connect the logic components assembled into a large-grained logic component.MACAO is made up of three parts: component listener, component container and component executor. Component listener is responsible for monitoring run-time components loading and cancellation requests, is also responsible for parsing the attribute information delivered from external service into the information of the component description. Component executor is responsible for the implementation of the component operations, it will make a different operating actions towards basic components and logic components. When execution requests, the component executor will find corresponding component examples according to unique identification in the component container, and will pass in which the parameters of the context. Component container is responsible for storing, and dynamically maintaining the description of component information and its instance during operation. The effective component description information, after parsing out by the component listener, will be placed into the component container, when the component is executed, its component instance are also saved. In addition, the thesis also implements two optional modules: run-time log monitor module and management module of component run-time status.Then, this thesis presents a Java language referenced prototype framework of MACAO component model as well as a visual development tool MACAO Studio for rapid development and deployment. MACAO Studio is a set of Eclipse-based development tool kits, is an integrated visual development environment for component-based application in the integration of development, assembly, maintenance, deployment, management and published. It also enables to accomplish the management of the component library and the connector library.Finally, MACAO middleware, a pervasive computing middleware using component-based and service-oriented approach, is put forward through combination of MACAO component model and service-oriented OSGi framework. MACAO middleware architecture consists of three main levels composition, namely, the physical layer, application layer and platform layer. The physical layer is a collection of all the hardware devices of pervasive computing environment. Application layer includes the collection of a number of applications, toolkits and other pervasive computing applications provided by MACAO middleware. Platform layer is the core part of pervasive computing middleware, which includes MACAO framework, OSGi framework, a variety of pervasive computing services, OSGi standard services as well as the OSGi bundles released by application layer and physical layer. This thesis also is designed to discuss how to expand and use of various pervasive computing services in the MACAO middleware through the research and design for dynamic update in pervasive computing service.In conclusion, this research can promote the application of pervasive computing middleware research, has certain theoretical significance and practical value. It provides valuable ways and means for research of the component-based service-oriented pervasive computing middleware and its integrated development environment.