Không bảo lãnh đáng tin cậy của mô hình Chiến lược Quyết định Sự kiện Chiến lược Sự kiện Chọn Monitor đốt Chiến lược chịu đựng lỗi chiến lược lỗi khoan dung siêu dữ liệu ưu đãi Profiler quản lý Khả năng Khả năng Không miễn phí Adapter Không miễn phí Chiến lược Chiến lược phục hồi phục hồi Chiến lược | TERMINAL SOFTWARE PLATFORM TECHNOLOGIES 223 Figure Reliability support in AOE by getting the current failure-free strategy first and then calling the desired method . doPost and doGet on the strategy. Recoverable Mervlets allow the same application to have different fault-tolerance mechanisms during different contexts. For example the Web Mail application may be configured to be more reliable for corporate e-mail than personal e-mail. Dynamic reconfigurability support in fault tolerance is achieved by allowing the two main components the RMS and the Recoverable Mervlet to have different failure-free and recovery strategies which can be set dynamically by the ARM shown in Figure . The separation between failure-free and recovery strategies helps in developing multiple recovery strategies corresponding to a failure-free strategy. For example in case of RMS one recovery strategy may prioritize the order in which messages are recovered while another recovery strategy may not. In our current implementation the adaptability in fault-tolerance support is reflected in the ability to dynamically switch on and off server-side logging depending on current server load. Under high server load the ARM can reconfigure the RMS to stop logging on the server side. In some cases this can result in marked improvement in the client perceived response time. Conclusions The evolution of handheld devices clearly indicates that they are becoming highly relevant in users everyday activities. Voice transmission still plays a central role but machine-to-machine interaction is becoming important and it is poised to surpass voice transmission. This data transmission is triggered by digital services running on the phone as well as on the network that allow users to access data and functionality everywhere and at anytime. 224 TERMINAL SOFTWARE PLATFORM TECHNOLOGIES This digital revolution requires a middleware infrastructure to orchestrate the services running on the handhelds to
