Geographic features change over time, this change being the result of some kind of event or occurrence. It has been a research challenge to represent this data in a manner that reflects human perception. Most database systems used in GIS are relational, and change is either captured by exhaustively storing all versions of data, or updates replace previous versions. This stems from the inherent difficulty of modelling geographic objects in relational tables. This difficulty is compounded when the necessary time dimension is introduced to model how those objects evolve. There is little doubt that the object-oriented (OO) paradigm holds significant advantages over the relational model when it comes to modelling real-world entities and spatial data, and we believe that this contention is particularly true when it comes to spatiotemporal data.
In this presentation we describe a generic, object-oriented model for representing spatiotemporal geographic data, called the Feature Evolution Model (FEM), based on a 'state-event-state' approach. The model is used to implement a Spatiotemporal Database Management System in Oracle Spatial, and a point-and-click interface is described that enables querying and visualisation.