In recent years, there has been a new understanding of how cities evolve and function, which reflects the emergent paradigm of complexity. The crux of this view is that cities are created by differentiated actors involved in individual, small-scale projects interacting in a complex way in the urban development process. This 'bottom up' approach to urban modeling not only transforms our understanding of cities, but also improves our capabilities of harnessing the urban development process. For example, we used to think that plans control urban development in an aggregate, holistic way, but...