Book excerpt: This book constitutes the refereed proceedings of the 14th International Conference on Database and Expert Systems Applcations, DEXA 2003, held in Prague, Czech Republic, in September 2003. The 91 revised full papers presented together with an invited paper and a position paper were carefully reviewed and selected from 236 submissions. The papers are organized in topical sections on XML, data modeling, spatial database systems, mobile computing, transactions, bioinformatics, information retrieval, multimedia databases, Web applications, ontologies, object-oriented databases, query optimization, workflow systems, knowledge engineering, and security.