“Search is an integral part of peoples’ online lives; people turn to search engines for help with a wide range of needs and desires, from satisfying idle curiousity to finding life-saving health remedies, from learning about medieval art history to finding video game solutions and pop music lyrics. Web search engines are now the second most frequently used online computer application, after email. Not long ago, most software applications did not contain a search module. Today, search is fully integrated into operating systems and is viewed as an essential part of most information systems.” (Marti A. Hearst)