Modelling changes and events in dynamic spatial systems with reference to socio-economic units

The large majority of current systems for handling geospatial information are static, concentrating on a single temporal snapshot, usually the current state. Changes in the application domain are tracked in the system by performing updates and erasing information on the past. In recent years there has evolved a body of research, both in the general database community (Snodgrass 1992) and in the spatial database community (Al Taha et al 1993) for adding temporal dimensions. That research addresses the issue of ‘time in the system’, where the challenge is to provide computational models that enable past, current and future states of the application domain (valid time) and the system (transaction time) to be handled in the temporal database.