This book constitutes the refereed proceedings of the 4th International Workshop on Databases in Networked Information Systems, DNIS 2005, held in Aizu-Wakamatsu, Japan in March 2005. The 17 revised full papers presented together with 8 invited papers were carefully reviewed and selected for inclusion in the book. The papers are organized in topical sections on information interchange and management systems, Web data management systems, networked information systems applications, and networked information systems implementations.