| Object Request Brokers (ORBs), which are building blocks of distributed object computing (DOC) middleware, have shown success in facilitating communications among object-based software in distributed, fixed-network environments. Devices in ubiquitous computing environments form webs of short-range and low-power mobile ad hoc networks to exchange information with each other. Application software systems in ubiquitous computing environments are usually context-sensitive; they take different actions adaptively in different contexts (e.g., location, time). Due to these characteristics, existing ORBs are not suitable for ubiquitous computing environments.; This dissertation presents research results for developing context-sensitive ORBs to provide context-sensitive communications among distributed object-based software in ubiquitous computing environments. Context-sensitive communications enable distributed objects to spontaneously interact with each other based on changes in specific contexts, rather than explicit instructions from the objects themselves.; First, a context-sensitive middleware framework is developed to facilitate context-triggered object activation. Second, an inter-ORB protocol is generated that is capable of dynamically discovering remote objects and providing inter-object communications in mobile ad hoc networks. Third, an energy-efficient inter-ORB protocol is developed for conserving the limited battery power of a device during object discovery. The research results have been applied to develop Reconfigurable Context-Sensitive Middleware Object Request Broker (R-ORB). Experimental results indicate that R-ORB is lightweight, energy-efficient, and has good performance for battery-powered handheld devices. |
