This book is the first coherently written multi-author monograph on Web Intelli gence (WI). It offers a thorough introduction and a systematic overview of the new field. It reflects the current state of the research and development in various areas of WI, as well as theoretical and application aspects of WI and Web-based intelligent information systems and services. It highlights several promising WI topics, which will impact on the development of the ultimate Wisdom Web. The book contains one introductory paper and 19 survey/research papers. The papers are structured into six parts: Web agents, Web mining and farming, Web information retrieval, Web knowledge management, the infrastructure for Web in telligent systems, and social network intelligence. We conceived and coined the notion Web Intelligence in late 1999. Back then although there was a variety of Web- or Internet-related conferences, journals, and books, none was devoted to the intelligence aspects of Web information systems and services. It was felt that there was a need for a conference, a journal, and/or books for researchers, scientists, and industry practitioners who wanted to publish and exchange ideas on Web Intelligence. At the 24th Annual International Computer Software and Applications Confer ence (IEEE COMPSAC) in 2000, we first introduced Web Intelligence. In 2001, the first Web Intelligence conference (WI 2001, http://kis.maebashi-it.ac.jp/wiOll) was successfully held in Maebashi, Japan.