Naturally there is a great deal of useful research exploring ways of using constraints in an object oriented programming environment, in databases, and on the internet. The field of constraint databases, in particular, has thrown up a growing community of researchers who are exploring the theoretical and practical possibilities of storing constraints in databases, imposing constraints on databases, and retrieving constraints from databases. This work is starting to be noticed in the field of geographical information systems. There is a growing need for databases to handle space, in two and three dimensions, and time. Examples are environmental monitoring and protection, air traffic control, and reasoning about motion in three dimensions. The constraint database technology appears to address these requirements.