Abstract
François Bourdoncle, co-founder of Exalead, presented the anatomy of a search engine, which comprises three sub-functions: fetching pages from the Internet, indexing them, and calculating and presenting answers to questions. The first search engine, Altavista, was housed in a large machine and indexed 100 million pages. Modern engines use thousands of PCs and index tens of billions of multilingual and soon multimedia pages. Page collection exploits the special "bow-tie" structure of the Web page graph, with large portals as referral centers. Indexing is based on efficient coding of reverse word-to-document lists. F. Bourdoncle explained the algorithms for building and consulting the index, as well as the calculation of page order in the response that has built Google's supremacy. Finally, he discussed the immense economic stakes involved.
