Efficient Techniques for Improving the Performance of Multimedia Search Engines

The main objective of the work presented in this thesis is to improve the performance of multimedia search engines. The contributions of the work presented are: First, a watcher based crawler (WBC) that has the ability of crawling static and dynamic websites has been introduced. In this crawler, a watcher file, which can be uploaded to the websites servers, prepares a report that contains the addresses of the updated and the newly added webpages. The watcher file not only allows the crawlers to visit the updated and the newly webpages, but also solves the crawlers overlapping and communication problems. In addition, the proposed WBC is split into five units, where each unit is responsible for performing a specific crawling process, and this will increase both the crawling performance and the number of visited websites. The second contribution of this thesis is presenting a new re-ranking approach based on the multimedia files contents and some user specific actions. The proposed reranking scheme has the ability of working with all multimedia types: video, image, and audio. In addition, a group of multimedia descriptors that can be extracted from the file concurrently using multiple threads, will be used to describe accurately the multimedia file. Furthermore, the proposed re-ranking approach can show the most relevant files to the top of the query results, and can increase the percentage of the retrieved relevant files. Third, we have proposed an efficient scheme for eliminating duplicated files in multimedia query results, and finally, the performance of the query by example (QBE) has been enhanced to efficiently support all multimedia types. Several experiments have been conducted to show the validity of the proposed approaches. Keywords: Multimedia search engines, Information retrieval, Crawling algorithm, Re-ranking algorithm, Elimination of duplicated files, Query by Example