Formal Modeling and Simulation of Availability-based Agent Behavior : Case Studies of Human Movement and Imitation

다국어 초록 (Multilingual Abstract)

In today’s high-tech age, the advancement of information and communications technology has played a significant role in solving some of the real-world problems in our societies. However, due to the nondeterministic behavioral patterns of human beings, the management of its complex dynamics remains a challenge. In particular, two factors hinder policymakers and researchers from applying various data-driven approaches to the management of social systems: i) many modern societies lack the long history and stable indices required for the reproduction of past trends, and ii) it is always time-consuming and expensive to accumulate sufficient data for complete analyses. To overcome these obstacles, specialists in modeling and simulation (M&S) recommended one practical approach, i.e., constructing a virtual model similar to the target system and analyzing its simulation outputs depending on the available information in a given situation. Agent-based modeling and simulation (ABMS) is an M&S technique that assembles autonomous and interacting decision makers (e.g., human beings, groups, and institutions) in an effort to simulate their collective behaviors. Recently, this technique has attracted attention as a new M&S paradigm, and its inconclusive theorization in representing human systems has disrupted the practical dissemination of ABMS for real-world problems.
The main goal of this study was to investigate a better framework for agent-based models that describe how people actually behave across interdisciplinary domains. As a step toward this far-reaching ambition, this study attempts to develop a modeling formalism that enables researchers to explore a truer agent-based representation of multidisciplinary human systems grounded in systems theory and ecological findings relating to human behavior. The target system is specified as the social and biophysical environments in which availability-based imitation and movement become manifested according to the affordance theory. The research scope is limited to illustrations of two fundamental actions of human beings in three different application domains, namely, pedestrian dynamics (in physical space), nuptiality dynamics (in social space), and evacuation dynamics (in integrated space).
To this end, the study is composed of three parts: i) a literature review pertaining to modeling formalisms for human systems in the context of ABMS, ii) the development of a formalism based on the latest findings in M&S engineering and cognitive sciences, and iii) three illustrations of the developed formalism and plausibility tests of the simulated dynamics. The first segment presents the research background for understanding the full details of the proposed formalism, including the concept of ABMS, its theoretical trends in representing human behaviors, affordance theory, and formalisms for multicomponent systems. In summary, well-cited studies pertaining to the concepts, structures, and terminologies of ABMS are surveyed for general scholarly sentiments regarding them. In particular, the review also highlights the latest findings in the theory of affordances and formalisms, which have been incorporated in predecessors to this research. The second segment explains the proposed formalism through two different perspectives based on the aforementioned theoretical foundations. It presents not only a conceptual framework for cognitive science and its related disciplines but also a mathematical template based on DEVS for M&S engineers. Subsequently, an illustration of pedestrian dynamics is implemented within an off-the-shelf M&S software (i.e., AnylogicTM) to enable easier reproductions and verify a default working mechanism of the proposed formalism. The last segment includes case studies on two different domains, namely, nuptiality and evacuation dynamics. The first section of this part develops an agent-based approach for exploring nuptiality dynamics and marriage heuristics in small-world networks. The other section demonstrates evacuation in a radiological emergency based on the fundamental social and physical behaviors (i.e., movement and imitation) of human beings. Plausibility test of the simulated output has also been conducted at the level of a proof-of-concept due to limited empirical evidence within the target system. At the beginning of each section, the research contexts of both applications are specified to clearly differentiate the proposed approaches.
The key novelty of this study is the incorporation of ecological findings on ubiquitous human behaviors into the latest modeling formalisms, which are specialized in ABMS, to fill the gap between the perspectives of cognitive scientists and M&S engineers. The developed formalism focuses on human nature in terms of accessible information rather than perfectly taking into account the entirety of a situation. It enables agent-based modelers to more clearly simulate the complex dynamics driven by the bounded rationality of human beings. The formalism could support the provision of an extensible digital twin for factories, cities, etc., in which multidisciplinary issues coexist. In conjunction with cyber-physical systems (CPS), human-in-the-loop (HITL), and other artificial intelligence (AI) technologies, it is anticipated for the proposed agent-based approach to contribute to a more convenient society for humans relying on automatic systems within themselves.

국문 초록 (Abstract)

ICT 기술 발전과 함께 다양한 문제들이 해결되고 있지만, 복잡한 사회 변화를 예측하고 제어하는 것은 여전히 도전적인 일이다. 특히, 인간 행동에 내포된 다양한 불확실성과 복잡성은 그들의 거동을 적절하게 산정하는 것을 더 어렵게 만들며, 누적된 자료가 부족하고 실험조차도 어려운 경우가 많아 대부분의 접근법에 제약이 생기게 된다. 이러한 제약을 극복하기 위해서, 시뮬레이션 모형 개발자들은 시스템을 적절하게 재현해서 모의 실험하는 것이 최선이라고 생각하며, 시스템을 행위자의 수준에서 구현하고 시연하는 것을 행위자 기반 모형화 및 시뮬레이션(ABMS)이라고 얘기한다. 사회 시스템을 위한 해당 접근의 필요성은 이미 광범위한 분야에서 확인되고 있으나, 아직까지 대다수의 연구가 각자의 문제 유형에 특화하여 개발하고 있어 기술적인 연계나 보편화에 제약을 받고 있다.
본 연구의 지향점은 여러 학문 분야를 포함하고 있는 사회 시스템의 ABMS를 위해 하나의 형식론(formalism)을 개발하는 것이다. ABMS의 이론적 정립을 위한 연구들이 각 분야별로 제시되고 있지만, 사회 시뮬레이션을 위한 통합된 모형화 형식론의 보급은 여전히 원대한 야심에 가깝다. 본 연구는 상기 목적을 향한 하나의 발걸음으로써, 인간 시스템의 행위자 기반 모형화를 위해 개발된 기존의 형식론과 개념적인 합치들을 조사하고, 이를 바탕으로 여러 도메인에서 나타나는 인간의 기본 행동 두 가지를 정형화된 모형으로 구현하는 것을 목표로 한다. 모사 대상은 어포던스(affordance)가 작동하는 사회-생물리적 환경(social and biophysical environment)에서 제한된 가용성에 따른 모방과 이동으로 선정하였으며, 이를 포함하는 물리 공간에서의 보행 역학 관계와 사회 공간에서의 혼인 상태 변화, 그리고 물리-사회 통합 공간에서의 소개 거동을 재현하는 것으로 연구 범위를 제한한다.
이를 위해 본 연구는 크게 세 가지 단계로 구성된다: (i) 형식론 개발을 위한 ABMS의 동향 조사, (ii) 최신 문헌을 반영한 형식론 제안 및 기본 구조 구현, 그리고 (iii) 상기 3가지 사례에 대한 제안된 형식론의 활용. 첫 번째 단계는 ABMS에 대한 고인용 문헌들을 중심으로 ABMS의 개념, 구조, 용어들의 이론적인 합치를 조사한다. 특히, 앞서 보고된 인간 시스템에 특화한 형식론에서 설계 근거로 활용한 어포던스 및 정형화 이론의 진보를 파악하고 검토하였다. 둘 째로, 앞서 파악한 이론적 기반을 토대로 하나의 모형화 형식론을 제시하였으며, 이를 인지과학자와 모델링 연구자 모두를 위해 개념적인 프레임워크와 DEVS (Discrete Event Simulation Specification) 기반의 정형 템플릿으로 나누어 설명하였다. 마지막으로, 본 연구는 해당 형식론이 실제로 두 개 이상의 도메인에서 활용될 수 있음을 확인한다. ABMS의 보편화를 위해 앞서 제시된 여러 프레임워크들이 각자의 도메인에 근거하여 물리적-사회적 상호작용 중 일부만을 모사하고 있는 반면, 본 연구에서는 보행, 혼인, 소개 거동에서 대표적인 물리 및 사회적 상호작용인 이동과 모방을 구현하고 타당성 시험(Plausibility test)을 수행하였다. 참고로, 위 모든 모형화와 시뮬레이션은 개인에게 무료로 배포되는 상용 소프트웨어(AnylogicTM)에서 구현하여 제안된 형식론의 활용을 돕고자 하였다.
본 연구의 가장 큰 특징은 인간 시스템에 특화한 모델링 형식론을 위해 보편적인 인간 행동에 대한 생태학적 개념들과 최신 DEVS 이론을 반영한 데 있다. 특히, 개발된 형식론에서는 많은 상황에서 완벽하게 계산하기보다 눈 앞의 정보에 따라 행동하는 인간의 특성이 보다 사실적으로 체계화되었다. 이를 통해, 개인의 제한된 합리성에 의한 시스템의 복잡 거동을 보다 명쾌하게 모사하고, 다학제의 주제를 동시에 담아야 하는 공장, 도시 등에 확장가능한 디지털 트윈 모형을 제공할 수 있을 것이다. 향후에는, CPS (Cyber-Physical System), HITL (Human-in-the-loop), 그리고 다른 AI 연구와의 연계와 함께, 자신 내부에 있는 자동 시스템에 의존하는 인간을 이해하고, 그들에게 사회 시스템을 보다 편리하도록 바꾸는 데 기여할 수 있을 것이라 기대한다.

목차 (Table of Contents)

• Abstract .................................................................................................................................................... i
• Abstract (in Korean) .............................................................................................................................. iii
• Table of Contents .................................................................................................................................... v
• List of Figures ....................................................................................................................................... vii
• List of Tables .......................................................................................................................................... x
• Acronyms and Abbreviations ................................................................................................................ xi
• Chapter 1. Introduction ........................................................................................................................... 1
• 1.1 Computational Modeling and Simulation for Human Systems .................................................... 1
• 1.2 What is Agent-based Modeling and Simulation?.......................................................................... 3
• 1.3 Problem Statement ........................................................................................................................ 6
• 1.3.1 Challenges in agent-based representations of human systems ............................................... 6
• 1.3.2 Research objectives ................................................................................................................ 8
• 1.4 Overview of the Dissertation ...................................................................................................... 10
• Chapter 2. Literature Review ................................................................................................................ 11
• 2.1 The Basic Concept of Agent-based Modeling and Simulation for Human Systems .................. 12
• 2.2 Trends in Agent-based Representation of Human Systems ........................................................ 16
• 2.2.1 Human decision-making models .......................................................................................... 16
• 2.2.2 Modeling formalisms for agent-based human systems ........................................................ 20
• 2.3 Affordance Theory ...................................................................................................................... 26
• 2.3.1 Affordances in ecological psychology ................................................................................. 26
• 2.3.2 Affordances in robot engineering ........................................................................................ 29
• 2.4 Parallel Formalism for Discrete Event System Specification ..................................................... 30
• 2.4.1 Discrete event system specification ..................................................................................... 30
• 2.4.2 Multicomponent-parallel discrete event system specification ............................................. 33
• Chapter 3. Formal Modeling of Availability-based Agent Behavior .................................................... 36
• 3.1 Proposal of an agent-based perspective on human systems ........................................................ 36
• 3.1.1 Vocabulary for common concepts ....................................................................................... 36
• 3.1.2 Conceptual framework for availability-based agent behaviors ............................................ 38
• 3.2 Formal Representation of Availability-based Agent Behavior ................................................... 40
• 3.3 Verification of Pedestrian Movement ......................................................................................... 45
• Chapter 4. Case Studies ........................................................................................................................ 52
• 4.1 Imitation Behavior with Individual Networks for Social Dynamics........................................... 52
• 4.1.1 Research context: agent-based computational demography ................................................ 53
• 4.1.2 Marriage heuristic models .................................................................................................... 54
• 4.1.3 Modeling of Demographic imitation on small-world networks ........................................... 58
• 4.1.4 Simulation and results .......................................................................................................... 70
• 4.1.5 Discussion ............................................................................................................................ 85
• 4.2 Fundamental Actions on Physical and Social Space under Emergency Evacuation .................. 88
• 4.2.1 Research context: simulating evacuations under radiological emergencies ........................ 88
• 4.2.2 Evacuation under radiological emergencies ......................................................................... 90
• 4.2.3 Modeling of evacuation behavior using availability-based heuristics ................................. 99
• 4.2.4 Demonstration of evacuation model .................................................................................. 104
• 4.2.5 Discussion .......................................................................................................................... 108
• Chapter 5. Conclusions ....................................................................................................................... 112
• 5.1 Research Contributions ............................................................................................................. 112
• 5.2 Limitations and Recommendations ........................................................................................... 114
• References ........................................................................................................................................... 118
• Appendix 1 .......................................................................................................................................... 134
• Appendix 2 .......................................................................................................................................... 138
• Acknowledgements ............................................................................................................................. 143