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The primary goal of this book is to present the research findings and conclusions of physicists, economists, mathematicians and financial engineers working in the field of 'Econophysics' who have undertaken agent-based modelling, comparison with empirical studies and related investigations. Most standard economic models assume the existence of the representative agent, who is "perfectly rational" and applies the utility maximization principle when taking action. One reason for this is the desire to keep models mathematically tractable: no tools are available to economists for solving non-linear models of heterogeneous adaptive agents without explicit optimization. In contrast, multi-agent models, which originated from statistical physics considerations, allow us to go beyond the prototype theories of traditional economics involving the representative agent. This book is based on the Econophys-Kolkata VII Workshop, at which many such modelling efforts were presented. In the book, leading researchers in their fields report on their latest work, consider recent developments and review the contemporary literature.

This article uses computer simulations as a means of assessing two different models for the competition between two languages from the interdisciplinary perspective of complex systems. These models allow for the analysis of the role of bilingual speakers and they consider two of the basic factors determining the use of each language: their relative prestige and the language loyalty of their speakers. Here we assess the effect of these parameters in different social networks, with the aim of contributing to the understanding of the role of bilingualism and social networks in processes of language contact. We first present a qualitative analysis based on a simulation tool that we have designed, in order to visualize the dynamics of the models. Secondly, we consider a qualitative analysis of the role of complex networks, identifying mechanisms for the rapid extinction of a language and for situations of language segregation. Finally, we present a quantitative analysis which shows, counter-intuitively, a transition from a final scenario of language maintenance to one of language shift as language loyalty increases. Other findings are: (i) that the scenario of language coexistence is reduced in the presence of bilingual agents; and (ii) that networks which allow for local effects reduce further the situations for which language maintenance is possible. ; In addition, for generous financial support, Xavier Castelló and Maxi San Miguel thank the Spanish Ministry for Science and Innovation and the European Regional Development Fund (grant FIS2007-60327, FISICOS), and Lucía Loureiro-Porto thanks the Autonomous Government of Galicia (INCITE grant 08PXIB204016PR) and the Spanish Ministry for Science and Innovation and the European Regional Development Fund (grants HUM2007–60706 and FFI2011-26693-C02-02). ; Peer reviewed

Decision makers in large scale interconnected network systems require simulation models for decision support. The behaviour of these systems is determined by many actors, situated in a dynamic, multi-actor, multi-objective and multi-level environment. How can such systems be modelled and how can the socio-technical complexity be captured? Agent-based modelling is a proven approach to handle this challenge. This book provides a practical introduction to agent-based modelling of socio-technical systems, based on a methodology that has been developed at Delft University of Technology and which has been deployed in a large number of case studies. The book consists of two parts: the first presents the background, theory and methodology as well as practical guidelines and procedures for building models. In the second part this theory is applied to a number of case studies, where for each model the development steps are presented extensively, preparing the reader for creating own models.

The provision of valuable e-government services depends upon the capacity to integrate the disperse provision of services by the public administration and thus upon the availability of interoperability platforms. These platforms are commonly built according to the principles of service oriented architectures, which raise the question of how to dynamically orchestrate services while preserving information security. Recently, it was presented an e-government interoperability model that preserves privacy during the dynamic orchestration of services. In this paper we present a prototype that implements that model using software agents. The model and the prototype are briefly described; an illustrative use case is presented; and the advantages of using software agents to implement the model are discussed. © Springer International Publishing Switzerland 2013.

AbstractThis article uses computer simulations as a means of assessing two different models for the competition between two languages from the interdisciplinary perspective of complex systems. These models allow for the analysis of the role of bilingual speakers and they consider two of the basic factors determining the use of each language: their relative prestige and the language loyalty of their speakers. Here we assess the effect of these parameters in different social networks, with the aim of contributing to the understanding of the role of bilingualism and social networks in processes of language contact. We first present a qualitative analysis based on a simulation tool that we have designed, in order to visualize the dynamics of the models. Secondly, we consider a qualitative analysis of the role of complex networks, identifying mechanisms for the rapid extinction of a language and for situations of language segregation. Finally, we present a quantitative analysis which shows, counter-intuitively, a transition from a final scenario of language maintenance to one of language shift as language loyalty increases. Other findings are: (i) that the scenario of language coexistence is reduced in the presence of bilingual agents; and (ii) that networks which allow for local effects reduce further the situations for which language maintenance is possible.

This paper is about the theoretical implications of agent-based modeling exercises. Construction of
an agent-based model challenges a social scientist to formalize many concepts and relationships
that would have remained implicit or unrecognized. While formalizing these "unimportant"
assumptions can be a nuisance, it can also have substantial theoretical payoffs. In order to fill the
gaps of the model, the researcher is forced to confront the gaps in the theory that motivated the
model in the first place. Using examples drawn from several large political science simulation
models, the paper argues that frailty, defined as unpredictability in the behavior of agents, is often
required in order to bring closure to the modeling exercise. It is difficult (or impossible) to square
the dynamic or aggregate implications of the agent-based model with observations without placing
a substantial amount of emphasis on frailty. Hence, the component in behavior that we often treat
as "error" in empirical analysis is actually a vital part of the glue that makes the many different
moving parts of a social system interact in coherent ways. The example models were developed
with the Swarm simulation system (http://www.swarm.org) during the last decade.

Although Agent Based Models (hereafter ABM) are now regularly reported in sociology journals, explaining the approach, describing models and reporting results leaves little opportunity to examine wider implications of ABM for sociological practice. This article uses an established ABM (the Schelling model) for this. The first part argues that ABM integrates qualitative and quantitative data distinctively, provides novel tools for understanding social causes and offers a significantly different perspective on theory building. The second part shows how the emerging ABM methodology is compatible with existing sociological practice while undermining several criticisms of ABM perceived to limit its sociological relevance.

An agent-based computer simulation demonstrates that results from Downs, Duverger, Riker, and Sundquist can be seen as emergent consequences of five simple rules about iteratively forming coalitions and adjusting policy platforms. The model creates distributions of agents who form coalitions within a political body. By modifying and omitting the basic rules, I compare results from plurality and majority-seeking actors and from policy-seeking, office-seeking, and mixed-strategy coalitions. A set of simple rules implemented by agents with extremely bounded knowledge are sufficient to drive the classic median voter, two-party system, minimum winning coalitions, and party realignment results in a single framework.

Social scientists associate agent-based simulation (ABS) models with three ideas about explanation: they provide generative explanations, they are models of mechanisms, and they implement methodological individualism. In light of a philosophical account of explanation, we show that these ideas are not necessarily related and offer an account of the explanatory import of ABS models. We also argue that their bottom-up research strategy should be distinguished from methodological individualism.

Current approaches to build social networking systems are based on a centralized architecture because it allows a simple browser-based user experience and makes easier and more efficient to implement many algorithms used in a social networking site (e.g., friend suggestion), However this kind of architecture has many drawbacks for its users, e.g., lack of privacy, lack of anonymity, risks of censorship and operating costs. This paper presents a system, called Blogracy, which uses widespread and stable peer-to-peer technologies, such as distributed hash tables and BitTorrent, for coping with intrinsic defects of centralized architectures and for being the basis of solid distributed social networking platforms. Moreover, Blogracy takes advantages of multi-agent systems for simplifying the implementation of social network services in a decentralized setting.