Agent Based Modeling and Simulation: An Informatics Perspective

The term computer simulation is related to the usage of a computational model in order to improve the understanding of a system's behavior and/or to evaluate strategies for its operation, in explanatory or predictive schemes. There are cases in which practical or ethical reasons make it impossible to realize direct observations: in these cases, the possibility of realizing 'in-machina' experiments may represent the only way to study, analyze and evaluate models of those realities. Different situations and systems are characterized by the presence of autonomous entities whose local behaviors (actions and interactions) determine the evolution of the overall system; agent-based models are particularly suited to support the definition of models of such systems, but also to support the design and implementation of simulators. Agent-Based models and Multi-Agent Systems (MAS) have been adopted to simulate very different kinds of complex systems, from the simulation of socio-economic systems to the elaboration of scenarios for logistics optimization, from biological systems to urban planning. This paper discusses the specific aspects of this approach to modeling and simulation from the perspective of Informatics, describing the typical elements of an agent-based simulation model and the relevant research.Multi-Agent Systems, Agent-Based Modeling and Simulation

Bibliometrics, Stylized Facts and the Way Ahead: How to Build Good Social Simulation Models of Science?

This paper discusses how stylized facts derived from bibliometric studies can be used to build social simulation models of science. Based on a list of six stylized facts of science it illustrates how they can be brought into play to consolidate and direct research. Moreover, it discusses challenges such a stylized facts based approach of modeling science has to solve.Bibliometrics, Stylized Facts, Methodology, Model Comparison, Validation

An Agent-Based Model of Mediterranean Agricultural Land-Use/Cover Change for Examining Wildfire Risk

Humans have a long history of activity in Mediterranean Basin landscapes. Spatial heterogeneity in these landscapes hinders our understanding about the impacts of changes in human activity on ecological processes, such as wildfire. The use of spatially-explicit models that simulate processes at fine scales should aid the investigation of spatial patterns at the broader, landscape scale. Here, we present an agent-based model of agricultural land-use decision-making to examine the importance of land tenure and land use on future land cover. The model considers two 'types' of land-use decision-making agent with differing perspectives; 'commercial' agents that are perfectly economically rational, and 'traditional' agents that represent part-time or 'traditional' farmers that manage their land because of its cultural, rather than economic, value. The structure of the model is described and results are presented for various scenarios of initial landscape configuration. Land-use/cover maps produced by the model are used to examine how wildfire risk changes for each scenario. Results indicate that land tenure configuration influences trajectories of land use change. However, simulations for various initial land-use configurations and compositions converge to similar states when land-tenure structure is held constant. For the scenarios considered, mean wildfire risk increases relative to the observed landscape. Increases in wildfire risk are not spatially uniform however, varying according to the composition and configuration of land use types. These unexpected spatial variations in wildfire risk highlight the advantages of using a spatially-explicit agent-based model of land use/cover change.Land Use/Cover Change, Land Tenure, Wildfire, Mediterranean-Type Ecosystem, Agriculture, Spatial Heterogeneity

4-(4-Nitrophenoxy)biphenyl

The two phenyl rings of the biphenyl unit of the title compound, C18H13NO3, are almost coplanar [dihedral angle 6.70 (9)°]. The nitrophenyl ring, on the other hand, is significantly twisted out of the plane of the these two rings, making dihedral angles of 68.83 (4)° with the middle ring and 62.86 (4)° with the end ring. The nitro group is twisted by 12.1 (2)° out of the plane of the phenyl ring to which it is attached. Key indicators: single-crystal X-ray study; T = 173 K; mean σ(C–C) = 0.002 A° ; R factor = 0.040; wR factor = 0.118; data-to-parameter ratio = 12.8

'What Science Says is Best': Parenting Practices, Scientific Authority and Maternal Identity

Based on research in London with mothers from a breastfeeding support organisation this paper explores the narratives of women who breastfeed \'to full term\' (typically for a period of several years) as part of a philosophy of 'attachment parenting', an approach to parenting which validates long term proximity between child and care-taker. In line with wider cultural trends, one of the most prominent \'accountability strategies\' used by this group of mothers to explain their long-term breastfeeding is recourse to scientific evidence, both about the nutritional benefits of breastfeeding and about the broader cognitive and developmental benefits of attachment parenting more broadly. Women\'s accounts internalize and reflect popular literature around attachment parenting, which is explored here in-depth as a means of contextualizing shifting patterns of \'scientisation\'. What follows is a reflection on how \'scientific evidence\' is given credence in narratives of mothering, and what the implications of this are for individuals in their experience of parenting, and for society more broadly. As a form of \'Authoritative Knowledge\' (Jordan 1997) women utilise 'science' when they talk about their decisions to breastfeed long-term, since it has the effect of placing these non-conventional practices beyond debate (they are simply what is \'healthiest\'). The article therefore makes a contribution to wider sociological debates around the ways in which society and behaviour are regulated, and the ways in which \'science\' is interpreted, internalized and mobilized by individuals in the course of their \'identity work\'.Parenting, Psychology, Neuroscience, Scientific Authority, Maternal Identity

Governing Low Profile Issues: A Frame Analysis of Drug Addiction in a Local Setting

Frame analysis was developed by Erving Goffman as a sociological concept, used for understanding how individual actors relate themselves to the world, creating coherent frames out of individual social experiences. We apply frame analysis in the emergent field of sociology of governance, using the example of low profile public issue of drug addiction in a specific local social and political context of a municipality in Bosnia and Herzegovina, in order to understand the roles of governance actors and their social interactions in the attribution of meaning. We focus on mental organization of governance experiences related to drug addiction and the strategic involvement of different governance actors which use given frames. We discuss the importance of frame coherence and ways in which it can be achieved for the low profile issues.Frame Analysis, Sociology of Governance, Low Profile Issues, Frame Coherence

Dilbert-Peter Model of Organization Effectiveness: Computer Simulations

We describe a computer model of general effectiveness of a hierarchical organization depending on two main aspects: effects of promotion to managerial levels and efforts to self-promote of individual employees, reducing their actual productivity. The combination of judgment by appearance in the promotion to higher levels of hierarchy and the Peter Principle (which states that people are promoted to their level of incompetence) results in fast declines in effectiveness of the organization. The model uses a few synthetic parameters aimed at reproduction of realistic conditions in typical multilayer organizations. It is shown that improving organization resiliency to self-promotion and continuity of individual productiveness after a promotion can greatly improve the overall organization effectiveness.Organization Productivity, Peter Principle, Agent Based Modeling

Simulating the Effect of Social Influence on Decision-Making in Small, Task-Oriented, Groups

This paper describes a simulation study of decision-making. It is based on a model of social influence in small, task-oriented, groups. A process model of dyadic social influence is built on top of a dynamic model of status and task participation that describes the emergence of a stable power and prestige order. Two models of group decision-making are examined: a static model for which the beliefs of actors do not change, and a process model for which they do as a function of the standing of each member of each interacting pair in the evolving power and prestige order. The models are compared on a set of N=111 cases, each requiring an affirmative or negative group response to a proposition A(c) that pertains to a case c. Initial beliefs are assigned to each of five members of distinct professions based on an analysis of independently collected behavioral data pertinent to the proposition to be affirmed or denied in each case. Although the two influence models yield identical decisions in 70% of the cases examined, the differences between them are statistically significant and in several instances show a medium effect size. Most importantly, the differences can be explained in terms of social influence and the status and task participation model on which it depends.Social Influence; Decision Processes; Social Networks; Group Dynamics; Simulation; Agent-Based Modeling

Is Your Model Susceptible to Floating-Point Errors?

This paper provides a framework that highlights the features of computer models that make them especially vulnerable to floating-point errors, and suggests ways in which the impact of such errors can be mitigated. We focus on small floating-point errors because these are most likely to occur, whilst still potentially having a major influence on the outcome of the model. The significance of small floating-point errors in computer models can often be reduced by applying a range of different techniques to different parts of the code. Which technique is most appropriate depends on the specifics of the particular numerical situation under investigation. We illustrate the framework by applying it to six example agent-based models in the literature.Floating Point Arithmetic, Floating Point Errors, Agent Based Modelling, Computer Modelling, Replication