Book excerpt: This book constitutes the refereed proceedings of the 4th International Conference on Web-Age Information Management, WAIM 2003, held in Chengdu, China in August 2003. The 30 revised full papers and 16 revised short papers presented together with 2 invited contributions were carefully reviewed and selected from 258 submissions. The papers are organized in topical sections on Web; XML; text management; data mining; bioinformatics; peer-to-peer systems; service networks; time series, similarity, and ontologies; information filtering; queries and optimization; multimedia and views; and systems demonstrations.