Urbanisation processes are results of a broad variety of actors or actor groups and their behaviour and decisions based on different experiences, knowledge, resources, values etc. The decisions done are often on a micro/individual level but resulting in macro/collective behaviour. In urban research the ‘city’ as subject of interest is increasingly understood as a complex system because of these complex relations and interactions of actors, with no coherent delineation, somehow robust and steady, but also dependent on many factors which are almost of no individual importance but might have a strong influence on the bigger system. Traditional scientific methods or theories often tried to simplify, not accounting complex relations of actors and decision-making. The introduction of computers in simulation made new approaches in modelling, as for example agent-based modelling (ABM), possible, dealing with issues of complexity. Also in urban research, computer simulation is becoming popular for more and more issues, aiming at a new understanding of urban systems.

The essay is based on some recent articles as well as some relevant websites. Due to the use of
ABM in many scientific fields and the relevance of complexity for a majority of science, there exists a huge number of scientific articles, books, tutorials etc. to these topics which doesn’t make it easy for a novice in the field to find the right literature. The literature used gives an optimistic outlook for the future of this methodology, although ABM is (still) seen very critical regarding its usefulness and explanatory power.