Geografia artificiale, geni e mutuo appoggio

I multi-agenti rappresentano oggi uno dei principali metodi per la validazione o confutazione di ipotesi o modelli complessi. Nell’ambito di diversi settori disciplinari, le teorie sulla vita artificiale (intesa come partecipazione o dinamiche di ecosistemi digitali) hanno ulteriormente rafforzato la struttura epistemologica e gli obiettivi della ricerca. Per la geografia, i multi-agenti rappresentano un metodo che consente – fra le tante altre cose – di produrre teorie sulla relazione intrinseca tra spazio, organismi ed ecosistemi. All’interno di questa cornice di riferimento, l’esperienza di ricerca descritta in queste pagine ha visto la definizione dei principi fondamentali di un modello di tipo vegetale che mira principalmente a produrre elementi utili alla riflessione sui rapporti tra organismi e spazio. Nel tentativo di produrre evidenze utili al dibattito sul gene egoista, il modello digitale ha messo in luce come la “vita” sia piuttosto caratterizzata da processi di collaborazione, mutua partecipazione e beneficio reciproco, come correttamente suggerito da Kropotkin. Una delle acquisizioni più importanti maturate con questo studio è quella dell’identificazione degli effetti significativi di condizionamento esercitato dallo spazio sulle dinamiche delle forme di vita. Si tratta di osservazioni che consentono di ipotizzare in modo speculativo la nozione di spazio o geografia artificiale

Chapter 22 Simulation Modeling as a Policy Tool

This chapter describes, justifies, presents the pros and cons of and illustrates the use of simulation modeling as a handy, cost-effective and agile tool for policymakers. Simulation modeling is flexible enough to accommodate different levels of detail, precision and time frameworks. It also serves the purpose of a concrete communication platform that facilitates scenario analysis, what-if alternatives and forward looking. We specifically define agent-based modeling within the larger simulation domain, provide a brief overview of other computation modeling methodologies and discuss the concepts of multiple models, verification, validation and calibration. The conceptual framework section closes with a discussion of advantages and disadvantages of using simulation modeling for policy at various stages of implementation. Finally, we present a panorama of actual applications of simulation modeling in policy, with an emphasis on economic analysis

Individual accessibility and segregation on activity spaces: an agent-based modelling approach

One of the main challenges of cities is the increasing social inequality imposed by the way population groups, jobs, amenities and services, as well as the transportation infrastructure, are distributed across urban space. In this thesis, the concepts of accessibility and segregation are used to study these inequalities. They can be defined as the interaction of individuals with urban opportunities and with individuals from other population groups, respectively. Interactions are made possible by people’s activities and movement within a city, which characterise accessibility and segregation as inherently dynamic and individual-based concepts. Nevertheless, they are largely studied from a static and place-based perspective. This thesis proposes an analytical and exploratory framework for studying individual-based accessibility and segregation in cities using individuals’ travel trajectories in space and time. An agent-based simulation model was developed to generate individual trajectories dynamically, employing standard datasets such as census and OD matrices and allowing for multiple perspectives of analysis by grouping individuals based on their attributes. The model’s ability to simulate people’s trajectories realistically was validated through systematic sensitivity tests and statistical comparison with real-world trajectories from Rio de Janeiro, Brazil, and travel times from London, UK. The approach was applied to two exploratory studies: São Paulo, Brazil, and London, UK. The first revealed inequalities in accessibility by income, education and gender and also unveiled within-group differences beyond place-based patterns. The latter explored ethnic segregation, unveiling patterns of potential interaction among ethnic groups in the urban space beyond their residential and workplace locations. Those studies demonstrated how inequality in accessibility and segregation can be studied both at large metropolitan scales and at fine level of detail, using standard datasets, with modest computational requirements and ease of operationalisation. The proposed approach opens up avenues for the study of complex dynamics of interaction of urban populations in a variety of urban contexts

Individual accessibility and segregation on activity spaces: an agent-based modelling approach

One of the main challenges of cities is the increasing social inequality imposed by the way population groups, jobs, amenities and services, as well as the transportation infrastructure, are distributed across urban space. In this thesis, the concepts of accessibility and segregation are used to study these inequalities. They can be defined as the interaction of individuals with urban opportunities and with individuals from other population groups, respectively. Interactions are made possible by people’s activities and movement within a city, which characterise accessibility and segregation as inherently dynamic and individual-based concepts. Nevertheless, they are largely studied from a static and place-based perspective. This thesis proposes an analytical and exploratory framework for studying individual-based accessibility and segregation in cities using individuals’ travel trajectories in space and time. An agent-based simulation model was developed to generate individual trajectories dynamically, employing standard datasets such as census and OD matrices and allowing for multiple perspectives of analysis by grouping individuals based on their attributes. The model’s ability to simulate people’s trajectories realistically was validated through systematic sensitivity tests and statistical comparison with real-world trajectories from Rio de Janeiro, Brazil, and travel times from London, UK. The approach was applied to two exploratory studies: São Paulo, Brazil, and London, UK. The first revealed inequalities in accessibility by income, education and gender and also unveiled within-group differences beyond place-based patterns. The latter explored ethnic segregation, unveiling patterns of potential interaction among ethnic groups in the urban space beyond their residential and workplace locations. Those studies demonstrated how inequality in accessibility and segregation can be studied both at large metropolitan scales and at fine level of detail, using standard datasets, with modest computational requirements and ease of operationalisation. The proposed approach opens up avenues for the study of complex dynamics of interaction of urban populations in a variety of urban contexts

Desire lines as a proxy of pedestrian preferences: a synthetic approach to public space configuration

En la pràctica de l'Arquitectura i de l'Urbanisme, han aparegut en les últimes dècades una creixent quantitat d'eines de simulació en àmbits com el de la representació, l'energia, el comportament estructural o el control i seguiment de l'obra. Moltes d’aquestes eines representen una evolució de metodologies existents mitjançant l'aplicació de la informàtica. Aquesta capacitat de simulació de la realitat física contrasta amb la dificultat que presenta la simulació del comportament dels usuaris dins dels edificis o les ciutats, degut al poc coneixement de la seva conducta en aquests àmbits. Els usos que les persones faran dels espais són una nebulosa de nocions intuïtives dins del procés creatiu dels qui conceben aquests espais. De la mateixa manera com un equip d'Arquitectes que està projectant un gratacels necessita saber el comportament dels materials, l'aspecte de l'edifici acabat o la planificació dels treballs, necessiten disposar d'eines per anticipar el comportament de les persones (treballadors, clients, vianants o habitants) dins els espais que projecten. Aquesta tesi vol obtenir, mitjançant un model basant en agents, una eina per poder anticipar els moviments de les persones en els espais que projecten Arquitectes, Urbanistes i Paisatgistes i d'aquesta manera obtenir espais més adequats a les necessitats dels usuaris. Per tal de definir aquest model del comportament dels vianants en l’espai públic, es parteix de l'observació de la presència en espais públics total o parcialment enjardinats d’unes zones mancades de vegetació on el ferm ha estat compactat per les petjades dels vianants, en forma de camins o de dreceres. Aquestes dreceres expliquen la lògica de formació de manera espontània per part dels usuaris d'aquests elements no planificats, coneguts en anglès com a "desire paths", en contraposició als camins formalment planificats

Assessing vulnerability and modelling assistance: using demographic indicators of vulnerability and agent-based modelling to explore emergency flooding relief response

Flooding is a significant concern for much of the UK and is recognised as a primary threat by most local councils. Those in society most often deemed vulnerable: the elderly, poor or sick, for example, often see their level of vulnerability increase during hazard events. A greater knowledge of the spatial distribution of vulnerability within communities is key to understanding how a population may be impacted by a hazard event. Vulnerability indices are regularly used – in conjunction with needs assessments and on-the-ground research – to target service provision and justify resource allocation. Past work on measuring and mapping vulnerability has been limited by a focus on income-related indicators, a lack of consideration of accessibility, and the reliance on proprietary data. The Open Source Vulnerability Index (OSVI) encompasses an extensive range of vulnerability indicators supported by the wider literature and expert validation and provides data at a sufficiently fine resolution that can identify vulnerable populations. Findings of the OSVI demonstrate the potential cascading impact of a flood hazard as it impacts an already vulnerable population: exacerbating pre-existing vulnerabilities, limiting capabilities and restricting accessibility and access to key services. The OSVI feeds into an agent-based model (ABM) that explores the capacity of the British Red Cross (BRC) to distribute relief during flood emergencies using strategies based upon the OSVI. A participatory modelling approach was utilised whereby the BRC were included in all aspects of the model development. The major contribution of this work is the novel synthesis of demographics analysis, vulnerability mapping and geospatial simulation. The project contributes to the growing understanding of vulnerability and response management within the NGO sector. It is hoped that the index and model produced will allow responder organisations to run simulations of similar emergency events and adjust strategic response plans accordingly

Scale matters: Variations in spatial and temporal patterns of epidemic outbreaks in agent-based models

Agent-based modellers frequently make use of techniques to render simulated populations more computationally tractable on actionable timescales. Many generate a relatively small number of “representative” agents, each of which is “scaled up” to represent some larger number of individuals involved in the system being studied. The degree to which this “scaling” has implications for model forecasts is an underdeveloped field of study; in particular, there has been little known research on the spatial implications of such techniques. This work presents a case study of the impact of the simulated population size, using a model of the spread of COVID-19 among districts in Zimbabwe for the underlying system being studied. The impact of the relative scale of the population is explored in conjunction with the spatial setup, and crucial model parameters are varied to highlight where scaled down populations can be safely used and where modellers should be cautious. The results imply that in particular, different geographical dynamics of the spread of disease are associated with varying population sizes, with implications for researchers seeking to use scaled populations in their research. This article is an extension on work previously presented as part of the International Conference on Computational Science 2022 (Wise et al., 2022)[1]

Heterogeneity in Agent-based models

Agent-based models are an incredibly flexible tool that among other things, allow modellers to capture heterogeneity in agent attributes, characteristics, and behaviours. This study defines heterogeneity in agent-based models as agent granularity: the level of description used to define the agent population. Consequently, this increased complexity can make the already challenging tasks of calibration and parameter identification, even more difficult. Although modellers recognise the significance of model calibration, the process of uniquely determining model input from any given model output is overlooked. This thesis proposes an impact of heterogeneity in agent-based models is parameter non-identification. To this end, this research conducts a thorough examination of agent heterogeneity by the comparative study of homogeneous and heterogeneous scenarios in agent-based models. Using an emotional contagion case study model and approximate Bayesian computation calibration, it finds that the introduction of heterogeneity results in inaccurate parameter calibration compared to the homogeneous case. This study proposes the inaccurate results as the consequence of a failure to uniquely distinguish the effect of additional parameters in the model. Furthermore, failing to identify model parameters limits the predictive or forecasting power of the agent-based model. A simple case study is used to demonstrate that the use of unidentifiable models to inform real-world governmental and social policies can lead to erroneous conclusions and potentially unsound interventions

La diversidad cultural del primer neolítico (VII cal. BP) en el mediterráneo occidental. Una análisis desde los sistemas complejos y la simulación basada en agentes

Esta tesis doctoral aborda el estudio de la variabilidad cultural del primer Neolítico en el Mediterráneo occidental partiendo de la hipótesis del autoestop cultural. En este contexto el principal objetivo ligado a la expansión del Neolítico que queremos contestar con la elaboración de la presente tesis doctoral es cuál fue el mecanismo o mecanismos de transmisión que afectaron en la formación de las culturas neolíticas del Mediterráneo occidental. Dicho de otro modo, nuestra intención es investigar si existe un patrón cultural claro que podría estar relacionado con una expansión desde el sur de Italia, y si dicha homogeneidad debe asociarse a la hipótesis del autoestop cultural "Cultural hitchhiking". Para abordar los objetivos formulados se han aplicado los conceptos propios de la teoría evolutiva y los Sistemas Complejos Adaptativos "CAS" ya que los postulados evolutivos permiten establecer las reglas y habilidades de los agentes así como las propias características de los CAS permitirá elaborar diferentes modelos con los que se obtendrán numerosos resultados para ser comparados con el registro arqueológico disponible. La metodología utilizada es la aplicación de las simulaciones computacionales, y más en concreto, los modelos basados en agentes. Estos resultan de especial interés en las ciencias humanas ya que sus propiedades los hacen realmente útil para plantear diferentes escenarios virtuales que serán cotejados con la información arqueológica. En definitiva, la tesis pone de manifiesto la importancia de integrar la modelización computacional como método dentro de la investigación prehistórica. Además. la investigación llevada a cabo resulta complementaria a los diferentes trabajos de investigación elaborados en torno a la expansión de los primeros grupos neolíticos en en Europa en general y en el Mediterráneo occidental en particular