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This dissertation, Secure Object Spaces for Global Information Retrieval (SOSGIR) by Yee-him, Cheung, 張貽謙, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled Secure Object Spaces for Global Information Retrieval (SOSGIR) submitted by Cheung Yee Him for the degree of Master of Philosophy at The University of Hong Kong in August 2000 With significant advancements in network infrastructure and computer technology, a tremendous amount of information is now available on the Internet. However, all the information sources are distributed so loosely that one may need to spend a long time surfing on the web blindly in order to, hopefully, find the required piece of information. Obviously, information retrieval technology has failed to keep up with the development of high-speed networks and the explosion of information contents. At present, information retrieval on the Internet involves two steps: (a) Locating potential information sources. By submiting keywords to a centralized search engine, a list of sites will be returned. (b) Exploring each potential site further. There are many disadvantages in the above scheme. First, as the number of web pages is growing rapidly, the cost for maintaining such a centralized index is very high. In general, the web coverage of the search engines is not satisfactory. Since the indexing is very generic, the accuracy of the search results is low. Therefore, a lot of time is in fact wasted in exploring and filtering out the irrelevant sites. This thesis is a response to the challenge of integrating distributed and heterogeneous multimedia repositories seamlessly on the Internet. The idea of this research is similar to that of a news group. In a news group, users can post their questions and experts around the world can respond. After some time, users can check the newsgroup for answers without even knowing where the experts are. In this research, the newsgroup is replaced by an object space which can be regarded as a public 'object drawer'. Instead of passing plain messages, information seekers put their query objects into the space. Information providers periodically look up interested query objects from the space and give result objects in return. Rather than waiting passively, information providers now actively search for query objects. Such a revolutionary mechanism for information retrieval eliminates the need for a centralized index and takes the advantage of complete decoupling between information seekers and providers. Since object templates are designed specifically for different kinds of queries, the accuracy of search results is expected to be higher than simple keyword search. In order to support global access, the system also includes portal lookup services for locating and coordinating object spaces distributed worldwide. A security infrastructure based on public key crytography is also designed to prevent malicious attacks and to enhance billing and accessibility controls. Putting all the ingredients together, we have 'Secure Object Spaces for Global Information Retrieval' (SOSGIR). To illustrate the concept of SOSGIR, a prototype consisting of client application (InfoSpace Explorer), server, object space and portal lookup service is implemented. Property information is chosen as the context. The system supports multimedia and is highly scalable and flexible in accomodating new users. In general, it successfully integrates distributed repositories on the Internet and improves the efficiency of global information retrieval. DOI: 10.5353/th_b2986959 Subjects: In

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