An object-based urban simulation model for interactive visualisation

This paper will present a version of Wu and Websters' urban growth simulations (Webster and Wu 1997a 1997b, Wu and Webster 1998) re-worked using object-oriented (o-o) constructs. The key feature of these simulations is that they integrate cellular automata (CA) and traditional urban economic modelling paradigms. The transition rules that govern urban evolution articulate property rights economic theory and the simulated cities are optimal in the sense of being in social and spatial equilibrium. Here we describe how a CA model may be translated into an o-o data model for implementation in C++. The main object of the exercise is to simplify the structuring and scripting of a complex dynamic geo-computational model in order to facilitate network-based interactive visualisation in the future. CA simulations conventionally rely on an explicitly raster data model which is ill-suited to model editing or to the development of flexible and modifiable visual interfaces. Our o-o model , in contrast, hides the three dimensional arrays that model activities in space behind the class structures of a semantically rich modular programme. It also allows all the spatial analytical functions in the model to be coded as methods that are attributed to cell and super-cell class objects. The result should be a fast and flexible version of an essentially cellular urban growth model that is well adapted to modular development, customisation and implementation in a heterogeneous network environment.