Synchronisation Protocol

Synchronisation protocols ensure that at the end of the simulation each event has taken place in chronological order in its respective logical process. One distinguishes between asynchronous and synchronous protocols.
  • "Synchronously" means that all agents evaluate the same situation (which is frozen while the agents deliberate) and act on it, such that all actions are performed at the same time and change the situation at the same time.
  • "Asynchronously" means that every single agents evaluates the situation and acts on it before it is any other agent's turn to perceive and evaluate the situation and act on it (of course, this means that the simulation run depends on the sequence of agents, but this is, at least for most of the conceivable scenarios, more realistic than the synchronous alternative).

The latter can be subdivided:

  • All agents do their job one after the othereither in a predefinedor in random order, each of them changing the world immediately, such that the next agent can perceive the changes that the other agents made.
  • Agents are scheduled to act at some time in the future, where the time of the next event in which the agent acts depends on the current situation. In this case the order in which the agents act is neither predefined nor random but dynamically determined by the circumstances, this being perhaps the most realistic variant.

All of these variants produce artifacts some of which have been investigated, e.g.

  • Rainer Hegselmann (1996): Cellular Automata in the Social Sciences: Perspectives, Restrictions, and Artefacts. In: Hegselmann, Rainer; Mueller, Ulrich; Troitzsch, Klaus G., eds.: Modelling and Simulation in the Social Sciences from a Philosophy of Science Point of View. Dordrecht: Kluwer, pp. 209-230
  • José Manuel Galán, Luis R. Izquierdo, Segismundo S. Izquierdo, José Ignacio Santos, Ricardo del Olmo, Adolfo López-Paredes and Bruce Edmonds (2009): Errors and Artefacts in Agent-Based Modelling. In: Journal of Artificial Societies and Social Simulation vol. 12, no. 1 1 <>
  • Barry G. Lawson and Steve Park (2000): Asynchronous Time Evolution in an Artificial Society Mode. In: Journal of Artificial Societies and Social Simulation vol. 3, no. 1, <>

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