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Cellular Automata. Spatio-Temporal Information for Society Münster, 2013. System Theory. Advantages Simple representation of the world Visual representation Modular and hierarchical Disadvantages No heterogeneity Implicit spatial representation Fixed connections between stocks.
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Cellular Automata Spatio-Temporal Information for Society Münster, 2013
System Theory Advantages • Simplerepresentationofthe world • Visual representation • Modular andhierarchical Disadvantages • No heterogeneity • Implicitspatialrepresentation • Fixed connections between stocks
Cellular Automata Firstly developed by Hungarian mathematician John von Neumann, who proposed a model based on the idea of logical systems that were self-replicating.
Basic Cellular Automaton • Grid of cells • Neighbourhood • Finite set of discrete states • Finite set of transition rules • Initial state • Discrete time
2-Dimensional Automaton A 2-dimensional cellular automaton consists of an infinite (or finite) grid of cells, each in one of a finite number of states. Time is discrete and the state of a cell at time t is a function of the states of its neighbors at time t-1.
Neighborhood and Rules Neighbourhood Rules Space and Time t States t1 Each cell is autonomous and change its state according to its current state and the state of its neighborhood.
www.terrame.org “CAs contain enough complexity to simulate surprising and novel change as reflected in emergent phenomena” (Mike Batty)
CellularSpace • A CellularSpace is a set of Cells. • It consists of an area of interest, divided into a regular grid. world = CellularSpace{ xdim= 5, ydim= 5 } forEachCell(world, function(cell) cell.value = 3 end)
Neighborhood • A Neighborhood represents the proximity relations of a cell. world:createNeighborhood{ strategy = "moore", self = false } Von Neumann Moore
Legend Defines colors to draw the Cells of a CellularSpace. Can be used with map observers. coverLeg = Legend { grouping = "uniquevalue", colorBar = { {value = 0, color = "white"}, {value = 1, color = "red"}, {value = 2, color = "green”} } }
Synchronizing a CellularSpace • TerraME can keep two copies of a CellularSpace in memory: one stores the past values of the cells, and another stores the current (present) values of the cells. • The model equations must read the past copy and write the values to the present copy of the cellular space. • At the correct moment, it will be necessary to synchronize the past copy with the current values of the cellular space.
Characteristics of CA models Self-organising systems with emergent properties: locally defined rules resulting in macroscopic ordered structures. Massive amounts of individual actions result in the spatial structures that we know and recognise;
Which Cellular Automata? For realistic geographical models the basic CA principles too constrained to be useful Extending the basic CA paradigm From binary (active/inactive) values to a set of inhomogeneous local states From discrete to continuous values (30% cultivated land, 40% grassland and 30% forest) Transition rules: diverse combinations Neighborhood definitions from a stationary 8-cell to generalized neighbourhood From system closure to external events to external output during transitions
