Development and use of simulation models in Operational Research : a comparison of discrete-event simulation and system dynamics

摘要

The thesis presents a comparison study of the two most established simulation approaches in Operational Research, Discrete-Event Simulation (DES) and System Dynamics (SD). The aim of the research implemented is to provide an empirical view of the differences and similarities between DES and SD, in terms of model building and model use. More specifically, the main objectives of this work are: 1. To determine how different the modelling process followed by DES and SD modellers is. 2. To establish the differences and similarities in the modelling approach taken by DES and SD modellers in each stage of simulation modelling. 3. To assess how different DES and SD models of an equivalent problem are from the users’ point of view. In line with the 3 research objectives, two separate studies are implemented: a model building study based on the first and second research objectives and a model use study, dealing with the third research objective. In the former study, Verbal Protocol Analysis is used, where expert DES and SD modellers are asked to ‘think aloud’ while developing simulation models. In the model use study a questionnaire survey with managers (executive MBA students) is implemented, where participants are requested to provide opinions about two equivalent DES and SD models. The model building study suggests that DES and SD modelling are different regarding the model building process and the stages followed. Considering the approach taken to modelling, some similarities are found in DES and SD modellers’ approach to problem structuring, data inputs, validation & verification. Meanwhile, the modellers’ approach to conceptual modelling, model coding, data inputs and model results is considered different. The model use study does not identify many significant differences in the users’ opinions regarding the specific DES and SD models used, implying that from the user’s point of view the type of simulation approach used makes little difference if any. The work described in this thesis is the first of its kind. It provides an understanding of the DES and SD simulation approaches in terms of the differences and similarities involved. The key contribution of this study is that it provides empirical evidence on the differences and similarities between DES and SD from the model building and model use point of view. Albeit the study does not provide a comprehensive comparison of the two simulation approaches, the findings of the study, provide new insights about the comparison of the two simulation approaches and contribute to the limited existing comparison literature.