Mobile Query Mechanism Based On Proxy Mailbox

Currently,research and implementation of mobile database is a hotspot in the fields of database and mobile computing. With the development of integrated circuit and mobile communication technologies,mobile database products will have great growth in user demand.Research is mainly focus on replication&caching,location management,query&optimizing,data broadcast,security,mobile transaction and human-machine interface technologies. Among these topics research of mobile query is one of the key technologies.The wide differences between mobile computing environment and static distributed computing environment make the traditionary client server model not suitable. It is necessary to set up a new mobile query model.In this thesis we first introduced the development of mobile computing model and adaptation techniques in recent years,and the application of mobile browsing web. Then we discussed the status of mobile query model in detail. After analyzing some models,we present our new three-tier mobile query model based on proxy and mailbox. The main contribution of this thesis includes:1. We defined a query proxy with an adaptation framework,a session protocol for exchanging data and context information between users and proxy. Through these works we make the model be able to support offline query and customized query.2. We defined a mailbox mechanism in the fixed network. When a user is disconnected,mailbox is responsible for encapsulating the query result and caching. This capability is nessesary for offline query support. In the aspect of mail passing,we proposed two kind of services,which are client pull and server push. For enery effiency in server push we provided two mail message-passing algorithms,they are algorithm based on time slot and algorithm based on statistics. Then we created arithmetic model under certain net architecture and related premises.Finally we discussed some topics in the deployment of mobile query application platform and proposed an object-oriented programming model and implemetation of some components.