Entities and Relations for Agent-Based Modelling ofComplex Spatial Systems

March/09

Pedro Ribeiro de Andrade

Antônio Miguel Vieira Monteiro

Gilberto Câmara

source: IGBP

The fundamental question of our time

How is the Earth’s environment changing, and what are the consequences for human civilization?

How to model these phenomena?

Agents as basis for complex systems

Agent: flexible, interacting, and autonomous

An agent is any actor within an environment, any entity that

can affect itself, the environment, and other agents.

Agent-Based Modelling

Goal

Environment

Representations

Communication

Action

Perception

Communication

source: Nigel Gilbert

“... Incorporating real spatial heterogeneity into agent-based models will improve our ability to draw conclusions about the behavior of complex systems in realistic environments...”

(Brown et al., 2005)

How can geospatial data feed agent-based models?

Scientific question

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Relations

Entities

How can geospatial data feed agent-based models?

Scientific question

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Citizens (points) Farmers (polygons)

First Entity: Agent

Source: (Crooks, 2006); (Lim et al. 2002)

Agents are computational systems placed in some environment.

(Jennings et al., 98)

Second Entity: Space

� Discrete → cells

� Dynamic

Agent

Cell

Cell Agent

Sources: (Benenson and Torrens, 2005; Samuelson and Macau, 2006)

FromTo

Relations

Cell→cell

Spatial neighbourhood between cells

Cell→agent

“Which agents belong to this cell?”

Agent→cell

Source: Adapted from (Lim et al. 2002)

“Which cells this agent controls, owns, targets?”

Agent→agent

Agents can communicate, exchange goods, etc.Agents are situated in space.

Agent

Cell

Cell AgentFromTo

Relations and their differences

Relations and their differences

--Adjacency, contiguity, distance, accessibility,

visibility

Amount of time, intimacy, emotional intensity, reciprocal services

Weight

SymmetricalSymmetricalDiredtedDirectedGraph

BinaryBinaryWeightedWeightedType

No flowNo flowAgents, suppliesInformationFlow

Cell→AgentCell→AgentCellsAgents

PlacementNeighbourhood

Agent

Cell

To

Neighbourhood

Cell AgentFrom

Relations and their differences

--Adjacency, contiguity, distance, accessibility,

visibility

Amount of time, intimacy, emotional intensity, reciprocal services

Weight

SymmetricalSymmetricalDiredtedDirectedGraph

BinaryBinaryWeightedWeightedType

No flowNo flowAgents, suppliesInformationFlow

Cell→AgentCell→AgentCellsAgents

PlacementNeighbourhood

Agent

Cell

To

PlacementCell AgentFrom

Source: (Benenson; Torrens, 2005), (Samuelson; Macau, 2006)

The idea of Generalized Proximity Matrix (GPM) is a foundation for setting up these relations

Hypothesis

Cell Agent

From

To

GPMGPM

GPMGPMAgent

Cell

Source: (Aguiar, 2003)

Which objects are closer?

Source: (Aguiar, 2003)

Which objects are closer?

Euclidean Spaces Open Network Closed Network

GPM – strategies for building relations

GPM as a graphTo

Agent

Cell

a

b

a

b

c

c

Cell Agent

From

Source: (Carneiro, 2006)

TerraME

Source: (Aguiar, 2003;; Carneiro, 2006)

� Cell

� CellularSpace

� Neighbourhood

� Trajectory

( , ≤≤≤≤ )

Space

Source: adapted from (Carneiro, 2006)

Deforestation > 70%

recently created

desfloresting

saturated

Latency > 6 years

Evolution of Desflorestation

recession

growing

normal

time = 1997

time = 1988

time = 1994

Economic system

Behaviour – Agent

CellAgent

ForEachCell

ForEachCellForEachNeighbor

CellularSpace

Trajectory

DBMS

CellAgent

ForEachAgent ForEachCell

ForEachCellForEachNeighbor ForEachNeighbor

ForEachAgent

CellularSpaceSociety

Group Trajectory

DBMS

Cell→agent

Model 1: Competition for Space

Cell→agent

Model 1: Competition for Space

Deforestation

Forest

Non-forest

Deforestation Map – 2000 (INPE/PRODES Project)

km

Projetos de Colonização

10

8

15

1614

13

Projetos antigosNovos projetosProjetos planejados

km

Projetos de Colonização

10

8

15

1614

13

Projetos antigosNovos projetosProjetos planejados

Projetos antigosNovos projetosProjetos planejados

Federal Government induced colonization area (since the 70’s):

� Small, medium and large farms.

� Mosaic of land use patterns.

� Definition of land units and typology of actors based on multi-temporal images (85-00) and colonization projects information (Escada, 2003).

Model 2: Deforestation in Rondônia

1985 to 1997

Source: adapted from (Carneiro, 2006)

Model 2: Deforestation in Rondônia

Large farmer (25 cells)

500 m (all)

Small farmer (2 cells)

Agent→cell

“Society”of

Producers

“Society”of

Suppliers

“Society”of

Consumers

GPM GPM

GPM GPM GPM

Model 3: Logistic or supply chains

Agent→agent

Conclusions

* Up to the modeller

Agent→CellCell→Agent

� Weak connections between toolkits and GIS

� Toolkits adapted for problems, or problems adapted to toolkits

Conclusions

Entities and Relations for Agent-Based Modelling ofComplex Spatial Systems

Pedro Ribeiro de Andrade

Antônio Miguel Vieira Monteiro

Gilberto Câmara

{pedro, miguel, gilberto}@dpi.inpe.br

http://lucc.ess.inpe.br