THIN, DISCONNECTED CLIENTS ON A HOSPITAL IT NETWORK

An application that supports a work-flow in a hospital puts special requirements on the system: 1. The application must be reliable. We can not risk any loss of the data. 2. The application should preferably execute on a hand held computer. The hospital workforce is mobile. 3. The application should be available and function continuously even though the hand held computer is periodically disconnected from the network. There may be some areas without network coverage. 4. The application must be able to exchange the data with servers on the fixed network automatically and transparently for users. There may be no time to go and synchronize the data. Creating a system that fulfills all these requirements is the challenge in this thesis. The mentioned requirements are shared by many other types of environments other than the hospital environment. Consequently, we see a use for a general system that supports creation of reliable applications for periodically disconnected hand held computers. In this thesis, we have clarified the concepts of how to build a client-server support system that combines the support for disconnections and support for reliability in one hand held device. We have performed a bottom-up analysis of the issues that arise when building such a system. We have also designed and implemented a prototype of a general client-server support system. The client-server support systems guarantees delivery of requests and responses. The system is able to sustain crashes and recover its state. The system is also able to handle varying degrees of connectivity that stretch from connected, intermittently connected to disconnected computers. We have demonstrated the general client-server system by building a hospital work-flow application using it. The application is a browser and the work-flow tasks are expressed in forms generated by a server. The server cooperates with a hospital IT system created by Radiometer A/S.