The Design And Implementation Of Image-Retrieval Prototype System Based On Mobile Agent

At present, Information Retrieval has been one of the most popular services in the Internet. As the development of the network technology and the expansion of the network scale, the quantity of the information has also been unimaginablly increased. How to get the accurate information which people are concerned with from the 'information ocean' is the duty of search engine. This thesis at first introduces the knowledge of search engine, including its history, its classification, and its theory. Several new tendency of the technology of the search engine are presented; especially the Mobile Agent technology is a perfect solution when deploying the distributed intelligent search engine.Mobile Agent is an emerging distributed computing technology. As a software entity, which migrates on networks and executes certain commission delegating certain user, Mobile Agent provides a new solution to carry out flexible distributed applications on dynamical changing, large-scale, heterogeneous networks. Comparing with the traditional distributed computing system mainly represented by client/server model, the characteristics and advantages of the mobile agent technology are shown. The thesis summarizes several key questions of the new technology such as naming, security, fault-tolerance and discusses mobile agent platform-Roamer, which has its own traits on the aspect of naming, security, migrating model.Then the thesis constructs an application frame of image retrieval based on mobile agent platform. Its goal is to provide a convenient way of the information search with the different units in the same field, for example, the medicine field. The function and the implementation of every part are carefully discussed. M-band integer wavelet transform is implemented in the searching module and it is used in picking up the image features. This method brings good results of image retrieval.Another important aspect of application constructing with mobile agent technology is the fault-tolerance. Even one node's fault may cause the whole commission to finish abnormally; a policy should be put forward to guarantee the recovery of the whole system from those faults or exceptions. The new 'double-backup' fault tolerant method, which is originated from sliding window method, is presented and its performance is carefully discussed. This new 'double-backup' fault tolerant method can satisfy the requirements and principles of information search area.