An Adaptive XML Data Broadcast Scheme In Mobile Computing Environment

As the wide-spread of XML in mobile computing, the requirement of efficiency of XML access and transmission are higher and higher. Therefore, how to effectively access and transmit XML documents in mobile computing environment becomes a hot research spot.Data broadcast is an efficient way for information dissemination in mobile computing environment. Among them, on-demand data broadcast is an efficient way for clients to get the personalized data according to their needs. Basing on an analysis of the XML query technique and on-demand data broadcast technology, an on-demand XML data broadcast model, namely C/D/S structure, is presented on a ground of group-based XML query and dispatch agent in the mobile computing environment. In addition, this paper puts forward a kind of adaptive XML on-demand broadcasting mechanism. On the server side, the XML documents branch is filtered firstly with superfluous parts pruned in accordance with the users' requests. And then by examine the system workload, the author uses (1, d) dynamic index structure and adaptive scheduling algorithm for data broadcasting to adjust the degree of data bucket. There is a group-based XML query and dispatch agent between the clients and server that divided the users' request into different groups. Then it schedules and dispatches the groups with the ratio of same prefix depth to server. After the acquisition of required data, the group-based XML query and dispatch agent will restore buckets to original XML documents which will be broadcasted to the corresponding clients.Finally, the proposed mechanism is evaluated by experimental simulation. The experimental results show that the prunings of redundant XML document branches can effectively improve bandwidth utilization. Through slight increments in average access time, the system can significantly shorten the average tuning time so as to greatly cut down the time spent in accessing and transmitting XML data by adaptive scheduling and XML query grouping process. To be added, the mechanism of XML data access and transmission is more favorable especially when considering the start-up and close WNI delay and insufficiency of network bandwidth.