Result Merging for Efficient Distributed Information Retrieval
by Kien T.E. Tjin-Kam-Jet
Centralized Web search has difficulties with crawling and indexing the Visible Web. The Invisible Web is estimated to contain much more content, and this content is even more difficult to crawl.
Metasearch, a form of distributed search, is a possible solution. However, a major problem is how to merge the results from several search engines into a single result list. We train two types of Support Vector Machines (SVMs): a regression model and preference classification model. Round Robin (RR) is used as our merging baseline. We varied the number of search engines being merged, the selection policy, and the document collection size of the engines. Our findings show that RR is the fastest method and that, in a few cases, it performs as well as regression-SVM. Both SVM methods are much slower and, judging by performance, regression-SVM is the best of all three methods. The choice of which method to use depends strongly on the usage scenario. In most cases, we recommend using regression-SVM.