A programming model and system support for disconnected-aware applications on resource-constrained devices

The emergence of networked lightweight portable computing devices can potentially enable accessibility to a vast array of remote applications and data. In order to cope with shortage of local resources such as memory, CPU and bandwidth, such applications are typically designed as a thin-client thick-server applications. However, another highly desirable yet conflicting requirement is to support disconnected operation, due to the low quality and high cost of on-line connectivity. We present a novel programming model and a runtime infrastructure that addresses these requirements by automatically reconfiguring the application to operate in disconnected mode of operation, when voluntary disconnection is requested, and automatically resorting to normal distributed operation, upon reconnection. The programming model enables developers to design disconnected aware applications by providing a set of component reference annotations with special disconnection and reconnection semantics. Using these annotations, designers can identify critical components, priorities, dependencies, local component alternatives with reduced functionality, and state merging policies. The runtime infrastructures carries out dis- and re-connection semantics using component mobility and dynamic application layout. The disconnected operation framework, FarGo-DA, is an extension of FarGo, a mobile component framework for distributed applications.