This volume contains the papers presented at the Fourth International Workshop on Database Machines. The papers cover a wide spectrum of topics including descrip tions of database machine implementations. analysis of algorithms and database machine components. architectures for knowledge management. recovery and con currency control issues. and solutions to the 110 bottleneck problem. As at the pre vious workshops in Florence. San Diego. and Munich. a diverse collection of coun tries. universities. research labs. and database machine vendors were represented by the authors and conference...