Different Modelling Purposes
How one builds, checks, validates and interprets a model depends on its ‘purpose’. This is true even if the same model is used for different purposes, which means that a model built for one purpose but now used for another may need to be rechecked, revalidated and maybe even rebuilt in a different way. Here we review some of the different purposes for building a simulation model of complex social phenomena, focussing on five in particular: theoretical exposition, prediction, explanation, description and illustration. The chapter looks at some of the implications in terms of the ways in which the intended purpose might fail. In particular, it looks at the ways that a confusion of modelling purposes can fatally weaken modelling projects, whilst giving a false sense of their quality. This analysis motivates some of the ways in which these ‘dangers’ might be avoided or mitigated.
KeywordsAnalogy Assumptions Bounding outcomes Calibration Data collection Education Explanation Generative explanation Guiding data collection Perturbation Plausibility Policy options Prediction Qualitative behaviour Question discovery Robustness Science Tradeoffs Training Understanding Validation
Many thanks to all those with whom I have discussed these matters, including Scott Moss, David Hales, Bridget Rosewell and all those who attended the workshop on validation held in Manchester.
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