Model Discovery Workshop at SSW
The generative, or mechanism-based, approach to modeling of social systems uses agent-based models (ABMs) to ‘grow’ the phenomenon under investigation. The modeler designs and implements the ABM, and chooses its parameters and initial conditions (i.e., inputs). Then the model is run to generate an emergent output – if this output can, in some sense, reproduce the phenomenon then it becomes a candidate explanatory model; otherwise it is rejected.
Whilst the ABM community is now focusing heavily on methodology for the consideration of model inputs (e.g, calibration techniques), surprisingly little attention is given to the consideration of model structure – i.e., the nature of the entities and equations in the ABM.
Whilst initiatives such as the Overview, Design concepts and Details (ODD) Protocol encourage modelers to articulate ABM structure in a thorough manner, these initiatives do not stimulate scientific consideration of the plurality at the heart of model structure selection decisions.
Where does a particular structure come from? Does it arise from the art of the modeler, or does it arise from a scientific process? How does ABM speak to theory, and vice versa? How do we choose between alternative mathematical and computational realizations of a specified mechanism, and when do we know that a mechanism can be rejected? What is special about the structure that has been identified, compared to the universe of other structures that could have been chosen? Do multiple, meaningful candidate structures exist and, if so, do these share any similarities.