The 4th International Conference on Mobile Data Management (MDM 2003) took place between the 21st and 24th of January 2003 at the Monash University Caulfield Campus in Melbourne, Australia. The conference highlighted a major issue in sensor networks, ubiquitous commerce and next generation communication services. Reflecting the wide spectrum of topics, the presentations of the selected papers were organized in nine sessions. The final session on Resource Discovery included papers on autonomous services for smart mobile devices, global location services and a spatial discovery service.