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--- geopro:pedro:models [2008/01/18 18:07] – 150.163.67.167
+++ geopro:pedro:models [2008/06/20 19:16] (atual) – pedro
@@ Linha 1: / Linha 1: @@
 ====== Agent-Based Models ======
+====An agent-based computational study of wealth distribution in function of resource growth interval using NetLogo====
+|R Damaceanu, 2008| Applied Mathematics and Computation 201:371–377| [[http://www.leg.ufpr.br/~pedro/papers/amc/wealth-distribution-resource-growth.pdf|pdf]]|
+\\
+**Abstract:** We describe an agent-based computational model that simulates the distribution of wealth in three classes: upper, middle and lower. The experimental data show us that: (1) the wealth of economy based on renewable resources is increasing if
+the resource growth interval is decreasing with the condition that the other factors remained unchanged; (2) the wealth of
+an economy based on renewable resources is higher in comparison with the wealth of an economy based on nonrenewable
+resources. This conclusion stresses the fact that the global economy must focus on using renewable resources because this
+approach may increase the global wealth.
+\\
+====Policy analysis from first principles====
+|S Moss, 2002| PNAS 99(3)7267–7274| [[http://www.leg.ufpr.br/~pedro/papers/pnas/policy-analysis-moss.pdf|pdf]]|
+{{  http://www.leg.ufpr.br/~pedro/figures/moss-sales-grid-size.jpg}}
+\\
+**Abstract:** The argument of this paper is predicated on the view that social
+science should start with observation and the specification of a
+problem to be solved. On that basis, the appropriate properties and
+conditions of application of relevant tools of analysis should be
+defined. Evidence is adduced from data for sales volumes and
+values of a disparate range of goods to show that frequency
+distributions are commonly fat-tailed. This result implies that **any
+stable population distribution will generally have infinite variance
+and perhaps undefined mean**. Models with agents that reason
+about their behavior and are influenced by, but do not imitate,
+other agents known to them will typically generate fat-tailed time
+series data. A simulation model of intermediated exchange is
+reported that is populated by such agents and yields the same type
+of fat-tailed time series and cross-sectional data that is found in
+data for fast moving consumer goods and for retail outlets. This
+result supports the proposition that **adaptive agent models of
+markets with agents that reason and are socially embedded have
+the same statistical signatures as real markets**. Whereas this
+statistical signature precludes any conventional hypothesis testing
+or forecasting, these models do offer unique opportunities for
+validation on the basis of domain expertise and qualitative data.
+Perhaps the most striking conclusion is that neither current social
+theory nor any similar construct will ever support an effective
+policy analysis. However, adaptive agent modeling is an effective
+substitute when embedded in a wider policy analysis procedure.
+\\
+====Constructing and Implementing an Agent-Based Model of Residential Segregation through Vector GIS====
+|A. T. Crooks, 2008| UCL Working Paper 133| [[http://www.leg.ufpr.br/~pedro/papers/abm-segregation-gis.pdf|pdf]]|
+\\
+**Abstract: ** In this paper, we present a geographically explicit agent-based model, loosely
+coupled with vector GIS, which explicitly captures and uses geometrical data and
+socio economic attributes in the simulation process. The ability to represent the
+urban environment as a series of points, line and polygons not only allows one to
+represent a range of different sized features such as houses or larger areas portrayed
+as the urban environment but is a move away from many agent-based models
+utilising GIS which are rooted in grid-based structures. We apply this model to the
+study of residential segregation, specifically creating a Schelling (1971, 1978) type
+of model within a hypothetical cityscape, thus demonstrating how this approach can
+be used for linking vector-based GIS and agent-based modelling. A selection of
+simulation experiments are presented, highlighting the inner workings of the model
+and how aggregate patterns of segregation can emerge from the mild tastes and
+preferences of individual agents interacting locally over time. Furthermore, the
+paper suggests how this model could be extended and demonstrates the importance
+of explicit geographical space in the modelling process.
+\\
+====Is Religion an Evolutionary Adaptation?====
+|J Dow,2008| Journal of Artificial Societies and Social Simulation  11(2)| [[http://jasss.soc.surrey.ac.uk/11/2/2.html|html]]|
+\\
+** Abstract:**   Religious people talk about things that cannot be seen, stories that cannot be verified, and beings and forces beyond the ordinary. Perhaps their gods are truly at work, or perhaps in human nature there is an impulse to proclaim religious knowledge. If so, it would have to have arisen by natural selection. It is hard to imagine how natural selection could have produced such an impulse. There is a debate among evolutionary scientists about whether or not there is any adaptive advantage to religion at all (Bulbulia 2004a; Atran and Norenzayan 2004). Some believe that it has no adaptive value itself and that it is just a hodge podge of of behaviors that have evolved because they are adaptive in other non-religious contexts. The agent-based simulation described in this article shows that a central unifying feature of religion, **a belief in an unverifiable world, could have evolved along side of verifiable knowledge**. The simulation makes use of an agent-based communication model with two types of information: verifiable information (real information) about a real world and unverifiable information (unreal information) about about an imaginary world. It examines the conditions necessary for the communication of unreal information to have evolved along side the communication of real information. It offers support for the theory that religion is an adaptive complex and it disputes the theory that religion is a byproduct of unrelated adaptive processes.
+\\
+The existence of gods, spirits, and the like cannot be verified by the senses. A belief in them makes no sense from an common evolutionary point of view. The animal whose conception of the world is out of touch with reality should be eliminated by natural selection. The one whose mental images correspond most closely to the real environment should be one to survive. The primary problem of explaining how religion has evolved through natural selection is the problem of explaining the belief in unreal things.
+The agents with whom an agent communicates can be chosen randomly from a uniform distribution of the agents, or they can be chosen from a distribution based on the tendency of another agent to engage in unreal communication.
+====Articulating land and water dynamics with urbanization: an attempt to model natural resources management at the urban edge====
+|R. Ducrot, C. Le Page, P. Bommel, M. Kuper, 2004| Computers, Environment and Urban Systems| [[http://www.leg.ufpr.br/~pedro/papers/ceus/water-dynamics.pdf|pdf]]|
+{{  http://www.leg.ufpr.br/~pedro/figures/water-dynamics.jpg?300}}
+**Abstract:** In a rapidly urbanizing world, population densities no longer allow for unlimited access to
+safe water. Competition for water, often associated with competition for the access to land,
+tends to be exacerbated in peri-urban areas. The objective of this paper is to propose a multiagent
+model prototype to represent the relationships between urbanization dynamics and land
+and water management in a peri-urban catchment area. A spatially explicit pilot model was
+developed using the Cormas platform. This prototype deals with a catchment that is the main
+drinking water reservoir and spring of a metropolitan area, and is subjected to high urban
+pressure and problems of pollution connected to land use and rain. The combined use of cellular
+automata, spatialized passive entities and communicating agents allows the articulation
+of the connections between hydrological processes (water cycle, pollution), land-use changes
+and urbanization. However, the representation is based on simplified dynamics and further
+work is needed to develop a simulation model that could be used as a discussion tool for land
+and water management at the urban edge.
+\\
+This work presents a simple model of agents. There is no real data, unless some temporal events such as crop cycles. It studies more the growth of favelas than the water dynamics per se.
+====Simulation of common pool resource field experiments: a behavioral model of collective action====
+|Daniel Castilloa, Ali Kerem Saysel, 2005| Ecological Economics|
+{{ http://www.leg.ufpr.br/~pedro/figures/laboratory-and-model.jpg}}
+\\
+**Abstract:** We investigate the decision rules adopted by individuals in local communities, whose livelihoods depend on common pool
+resource stocks and who face the cooperation dilemma in their everyday life. For this purpose, field experiments are modeled
+and the model structure and output are confronted with experimental data and with the relevant theory of collective action
+proposed by Ostrom (1998) [Ostrom, E., 1998. A behavioral approach to the rational choice theory of collective action.
+American Political Science Review 92 (1), 1–22.]. The field experiments analyze the cooperative action among coastal
+communities in Providence Island (Colombian Caribbean Sea). The simulation model is built according to the principles and
+methods of System Dynamics. The model formalizes the feedback causality among reputation, trust and reciprocity Ostrom
+(1998). Moreover, based on the payoff structure and treatments used in the experiments, it considers other
+behavioral factors such as temptation to free ride, profit maximization, awareness and risk perception of the individuals in
+feedback perspective. Model behavior replicates the patterns in the experimental data and is highly sensitive to reciprocity and
+free-riding behavior. It reveals path-dependent characteristic to the initial trust of the individuals in the group. The variables and
+decision rules built into the model structure provide the basis for a dialogue between the theories of collective action and future
+experimental designs to test and improve such theories.
+\\
+====Land use decisions in developing countries and their representation in multi-agent systems====
+|P Schreinemachers and T Berger, 2006| JLUS|
+\\
+**Abstract:** Recent research on land use and land cover change (LUCC) has put more emphasis on the importance of understanding the decision-making of human actors, especially in developing countries. The quest is now for a new generation of LUCC models with a decision-making component. This paper deals with the question of how to realistically represent decision-making in land use models. Two main agent decision architectures are compared. Heuristic agents take sequential decisions following a pre-defined decision tree, while optimizing agents take simultaneous decisions by solving a mathematical programming model. Optimizing behaviour is often discarded as being unrealistic. Yet the paper shows that optimizing agents do have important advantages for empirical land use modelling and that multi-agent systems (MAS) offer an ideal framework for using the strengths of both agent decision architectures. The use of optimization models is advanced with a novel three-stage decision model of investment, production, and consumption to represent uncertainty in models of land use decision-making.
+\\
+====The (Ir-)Relevance of the Crop Yield Gap Concept to Food Security in Developing Countries With an Application of Multi-Agent Modeling to Farming Systems in Uganda====
+|P. Schreinemachers, 2006| Thesis| [[http://hss.ulb.uni-bonn.de/diss_online/landw_fak/2006/schreinemachers_pepijn/|page]]|
+\\
+{{  http://www.leg.ufpr.br/~pedro/figures/population-network.jpg?600}}
+**Abstract:** This thesis scrutinizes the relationship between the width of the crop yield gap and
+farm household food security. Many researchers have argued that an exploitable gap
+between average crop yields and the genetic yield potential contributes to food
+security and that this potential should therefore be improved. Yet, crop yield gaps in
+developing countries are mostly wide, which is prima facie evidence that **factors
+other than the yield potential are most constraining**. [...]
+Multi-agent systems are used to model the heterogeneity in
+socioeconomic and biophysical conditions. The model integrates three components:
+(1) whole farm mathematical programming models representing human decision making;
+(2) spatial layers of different soil properties representing the physical
+landscape; and (3) a biophysical model simulating crop yields and soil property
+dynamics. The thesis contributes to methodology in four ways: First, it is shown that
+**MAS can be parametrized empirically from farm survey data**. Second, it develops a
+non-separable **three-stage decision model of investment, production, and
+consumption** to capture economic trade-offs in the allocation of scarce resources
+over time. Third, a three-step budgeting system, including an Almost Ideal Demand
+System, is used to simulate poverty dynamics. Fourth, coping strategies to food
+insecurity are included. [...]
+It is shown that the existence of maize yield gaps does not signal inefficiencies but poverty can be
+reduced substantially by addressing the underlying constraints such as access to
+innovations and credit. Improvements in labor productivity are crucial and are a
+much better indicator of development than crop yields and yield gaps. The results
+suggest that **a strong focus on crop yields and yield gaps might not only be
+inefficient but even counterproductive to development.**
+\\
+The author uses four programs for building his model: MatLab, STATA, MP-MAS and IBM-OSL (a library).
+//There is still no commercially available software for using MAS based on
+mathematical programming.//
+He used a sampling factor of 0.18, and Monte Carlo techniques to generate agent populations.
 ====Swarming methods for geospatial reasoning====
-|H. V. D. Parunak, S. A. Brueckner, R. Matthews, J. Sauter, 2006| IJGIS| pdf|
+|H. V. D. Parunak, S. A. Brueckner, R. Matthews, J. Sauter, 2006| IJGIS| [[http://leg.ufpr.br/~pedro/papers/ijgis/parunak_geospatial_reasoning_06.pdf|pdf]]|
 \\
@@ Linha 21: / Linha 211: @@
 \\
+Reasoning about the **movements of
+entities constrained by topological or topographical features**.
+Instead of reasoning logically about how entities might behave in a geospatial environment,
+we create models of the entities, situate them in a model of the environment,
+simulate their behaviour, and observe what they do.
 Swarming approach lends itself to implementation on parallel hardware,
@@ Linha 29: / Linha 225: @@
-^ number of walkers               | many agents to represent only one entity of the real world, in order to optimize the action |
+^ number of walkers                | many agents to represent only one entity of the real world, in order to optimize the action |
-^ walker's internal logic         | simple representation. the authors compares it with the BDI representation |
+^ walker's internal logic          | simple representation. the authors compares it with the BDI representation |
-^ stochasticity                   | do not always choose the best option. give a chance to the others |
+^ stochasticity                    | do not always choose the best option. give a chance to the others |
-^ stigmergic information exchange | **indirect communication**, mediated by a shared environment. advantages over message-based interaction: simplicity, scalability, robustness, and the ability to take advantage of environmental noise to support the need for stochrasticity in decision making|
+^ stigmergic information exchange  | **indirect communication**, mediated by a shared environment. A common form of stigmergy is the use by **ants** of chemical markers (**pheromones**) that they deposit and sense. Advantages over message-based interaction: simplicity, scalability, robustness, and the ability to take advantage of environmental noise to support the need for stochrasticity in decision making|
+Examples:
+  - searching for a minimum path with movement constraints (lots of agents to represent a single entity)
+  - surveillance system, where agents have to walk in order to cover the space (one to one representation)
+  - path based on environmental variables (direction and gradient)
@@ Linha 39: / Linha 245: @@
 \\
-**Abstract:** We present an agent-based model with the aim of studying how macro-level dynamics of spatial distances among interacting individuals in a closed space emerge from micro-level dyadic and local interactions. Our agents moved on a lattice (referred to as a room) using a model implemented in a computer program called P-Space in order to minimize their dissatisfaction, defined as a function of the discrepancy between the real distance and the ideal, or desired, distance between agents. Ideal distances evolved in accordance with the agent's personal and social space, which changed throughout the dynamics of the interactions among the agents. In the first set of simulations we studied the effects of the parameters of the function that generated ideal distances, and in a second set we explored how group macro-level behavior depended on model parameters and other variables. We learned that certain parameter values yielded consistent patterns in the agents' personal and social spaces, which in turn led to avoidance and approaching behaviors in the agents. We also found that the spatial behavior of the group of agents as a whole was influenced by the values of the model parameters, as well as by other variables such as the number of agents. Our work demonstrates that the bottom-up approach is a useful way of explaining macro-level spatial behavior. The proposed model is also shown to be a powerful tool for simulating the spatial behavior of groups of interacting individuals.
+**Abstract:** We present an agent-based model with the aim of studying how macro-level dynamics of spatial distances among interacting individuals in a closed space emerge from micro-level dyadic and local interactions. Our agents moved on a lattice (referred to as a room) using a model implemented in a computer program called P-Space in order to **minimize their dissatisfaction, defined as a function of the discrepancy between the real distance and the ideal, or desired, distance between agents**. Ideal distances evolved in accordance with the agent's personal and social space, which changed throughout the dynamics of the interactions among the agents. In the first set of simulations we studied the effects of the parameters of the function that generated ideal distances, and in a second set we explored how group macro-level behavior depended on model parameters and other variables. We learned that certain parameter values yielded consistent patterns in the agents' personal and social spaces, which in turn led to avoidance and approaching behaviors in the agents. We also found that the spatial behavior of the group of agents as a whole was influenced by the values of the model parameters, as well as by other variables such as the number of agents. Our work demonstrates that the bottom-up approach is a useful way of explaining macro-level spatial behavior. The proposed model is also shown to be a powerful tool for simulating the spatial behavior of groups of interacting individuals.
 \\
@@ Linha 160: / Linha 366: @@
 formation or segregation. In the most cases the system will arrive at a final state where both languages coexist. The results offer explanation
 for the existence and origin of synonymous in spoken languages.
 ====Modelling adaptive, spatially aware, and mobile agents: Elk migration in Yellowstone====
-{{  http://leg.ufpr.br/~pedro/figures/elk.jpg}}
 |D. A. Bennett and  W. Tang, 2006| IJGIS| [[http://leg.ufpr.br/~pedro/papers/ijgis/bennett_elk_migration_06.pdf|pdf]]|
@@ Linha 190: / Linha 397: @@
 of the landscape is not feasible.
-{{http://leg.ufpr.br/~pedro/figures/stknowledge.jpg  }}
+{{  http://leg.ufpr.br/~pedro/figures/stknowledge.jpg}}
@@ Linha 271: / Linha 478: @@
 One challenge with experimental research is how to assess whether laboratory subjects are representative
 of real-world actors.
@@ Linha 305: / Linha 513: @@
+====Groups of Agents with a Leader====
+|O Gigliotta, O Miglino and D Parisi, 2007| JASSS | [[http://jasss.soc.surrey.ac.uk/10/4/1.html|html]]|
+\\
+**Abstract:** We describe simulations of groups of agents that have to reach a target in a two dimensional environment, the performance criterion being the time taken by the last agent to reach the target. If the target is within a given distance from the agent, the agent moves towards the target; otherwise it moves randomly. The simulations contrast groups with and without a leader, where a leader is a member of the group which other members of the group follow as it moves through the environment. We investigate three factors that affect group performance: (1) group size; (2) the presence or absence of an individual agent with the ability to detect targets at a greater distance than those 'visible' to its companions; (3) the existence of a communication network among group members. The results show that, **in groups without communication, leaders have a beneficial effect on group performance, especially in large groups and if the individual with better than average sensory capabilities is the leader of the group. However, in situations where group members can communicate, these results are reversed, with leaders being detrimental, rather than beneficial, to group performance.**
+\\
+Primates [...] often have complex social hierarchies (Kummer 1971). When a group of primates moves together in the environment,
+specific individuals play a more important role than others in the initiation of movement and in the choice of the direction
+(Boinski and Garber 2000). Informal and formal social hierarchies are also a characteristic feature of human groups,
+so much so that there exists an entire academic discipline - political science - dedicated to social power in human societies.
+If it can detect the target, it goes directly to the target and ignores the leader. But if it can't, it moves in a
+direction which is halfway between (a) the direction it would have taken if it had chosen its direction randomly
+and (b) the current location of the leader.
+The presence of a leader allows the group to explore the environment in a more aggregate and therefore faster way.
+an individual with superior sensory capabilities is useful to the group only if it is also the leader of the group. :?::?: the paper does not explain why
+Communication:
+  - topology independent of spatial location
+  - based on some spatial radius
@@ Linha 466: / Linha 696: @@
 Each agent has a constant level of honesty and a risk-aversion level that changes over time.
 No interesting conclusions.
 ====Multi-agent simulation of group foraging in sheep: effects of spatial memory, conspecific attraction and plot size====