ESL: An Actor-Based Platform for Developing Emergent Behaviour Organisation Simulations

Specification and analysis of complex systems can be approached top-down or bottom-up [11]. A top-down approach conceptualises a system using a global state and the behaviour represented using an aggregated macro-behaviour of the system elements. For example, the System Dynamics (SD) model [8] uses the concepts of stocks, flows, feedback loops and time delays. A top-down approach considers a reductionist view [10] to understand system using the mathematical rigour from operational research, optimization theory, and sophisticated AI algorithms. A bottom-up approach, in contrast, considers the micro-behaviour of individual elements and their interactions. Conceptually, the bottom-up approach relies on emergentism [9] as advocated in actor model of computation [1], and agent-based systems [6]. Top-down approaches are a popular choice for analysing and understanding complex systems in the context of critical business needs such as decision making activities. Existing modelling and analysis tools that support top-down approaches are extremely efficient for describing and simulating the aggregated system behaviour. However, we propose that they are not appropriate for precise understanding of complex and dynamic systems that can only be understood in terms of emergent behaviour, for example systems that contain large numbers of socio-technical [7] elements having adaptive, autonomous and dynamic behaviours. Our recent work in this area [4, 2, 5, 3] has performed a domain analysis of organisations with socio-technical characteristics with a view to simulation and analysis leading to improved decisionmaking. This work has led us to choose a bottom-up approach for simulating emergent behaviour based on concepts represented using an actor-based model of computation. Our project has developed a conceptual model for simulation based on goals, measures, levers and adaptation and we are working on an actor-based simulation platform called ESL that supports these concepts. This tool demonstration will show features of ESL in terms of a real-world simulation.