Event-based modelling of ecological systems with asynchronous cellular automata

In this article, we give an example for the modelling of ecological systems with cellular automata based on the description of cell's behaviour by Petri nets. Petri nets offer a formal modelling technique with event-based, concurrent, asynchronous state changes where graphical symbols are used for the description of states with respect to stale changes. This allows the formal description of cellular automata with asynchronous cells' behaviour within one synchronous time phase of the automaton, i.e. within one time phase of the whole automaton, many asynchronous mini-steps of cells can appear. This can be, e.g. used to model moving individuals that cross an arbitrary number of cells within one time phase. By this attempt, a large class of individual-oriented models can be defined in a more abstract and formal manner than can be done by computer simulation programs. Since Petri nets allow a graphical representation of the modelled cells' behaviour, interactions, dependencies or cause effect chains can be visualized in the representation of the model. (C) 1998 Elsevier Science B.V. All rights reserved.