The annual international conference on Database and Expert Systems Applications (DEXA) is now well established as a reference scientific event. The reader will find in this volume a collection of scientific papers that represent the state of the art of - search in the domain of data, information and knowledge management, intelligent systems, and their applications. The 18th instance of the series of DEXA conferences was held at the University of Regensburg, Germany, September 3–7, 2007. Several collocated conferences and workshops covered specialized and comp- mentary topics to the main conference topic. Six conferences—the Eighth Inter- tional Conference on Data Warehousing and Knowledge Discovery (DaWaK), the Seventh International Conference on Electronic Commerce and Web Technologies (EC-Web), the Fifth International Conference on Electronic Government (EGOV), the 3rd International Conference on Trust, Privacy, and Security in Digital Business (TrustBus), the 3rd International Conference on Industrial Applications of Holonic and Multi-Agent Systems (HoloMAS), and the 1st International Conference on N- work-Based Information Systems (NBiS)—and 19 workshops were collocated with DEXA. The conference is a unique international event with a balanced depth and breadth of topics. Its much appreciated conviviality fosters unmatched opportunities to meet, share the latest scientific results and discuss the latest technological advances in the area of information technologies with young scientists and engineers as well as senior world-renown experts.