My research has addressed various aspects of spatial database research as well as related areas such as computational geometry and transportation research. He produced theoretical research results as well as practical work that are now used in actual applications and products. His early work focused on spatiotemporal databases and specifically on the modeling of such data as well as query optimization including indexing. He developed a spatiotemporal index, the TB-tree for trajectory data and a framework for capturing the uncertainty related to trajectory data and on query processing for moving objects’ data.