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5 Informal Approaches to Developing Simulation Models 63

be. Here the modelling is essentially a creative process, and the development of
the model proceeds in parallel with the development of the understanding of the
process; the model is itself a theory under development.
Thus, what often seems to happen in practice is that modellers start off in a phase
of exploratory modelling, where they don’t have a precise conception of the model
they want but a series of ideas and/or evidence they want to capture. They then may
develop the model in different directions, backtracking and changing their ideas as
they go. This phase continues until they think they may have a model or results that
are worth telling others about. This then is (or at least should be) followed by a
consolidation phase where the model is more rigorously tested and checked so that
reliable and clear results can be reported. In a sense what happens in this later phase
is that the model is made so that it is as if a more formal and planned approach had
been taken.
There is nothing wrong with having an exploratory approach to model devel-
opment. Unfortunately, it is common to see models and results that are publicly
presented without a significant consolidation phase being undertaken. It is very
understandable why a researcher might want to skip the consolidation phase: they
may have discovered a result or effect that they find exciting and not wish to go
through the relatively mundane process of checking their model and results. They
may feel that they have discovered something that is of more general importance;
however, this personal knowledge, which may well inform their understanding,
is not yet of a standard that makes it worthwhile for their peers to spend time
understanding, until it has been more rigorously checked.
One of the problems with the activity of modelling is that it does influence
how the modeller thinks. Paradoxically, this can also be one of the advantages
of this approach. After developing and playing with a model over a period of
time, it is common to “see” the world (or at least the phenomena of study) in
terms of the constructs and processes of that model. This is a strong version of
Kuhn’s “theoretical spectacles” (Kuhn 1969). Thus, it is common for modellers to
be convinced that they have found a real effect or principle during the exploration of
a model, despite not having subjected their own model and conception to sufficient
checking and testing—what can be called modelling spectacles. Building a model
in a computer is almost always in parallel with the development of one’s ideas about
the subject being modelled. This is why it is almost inevitable that we think about
the subject in terms of our models—this is at once a model’s huge advantage but
also disadvantage. As long as one is willing to be aware of the modelling spectacles
and be critical of them, or try many different sets of modelling spectacles, the
disadvantage can be minimised.
Quite apart from anything, presenting papers with no substantial consolidation
is unwise. Such papers are usually painfully obvious when presented at workshops
and easily criticised by referees and other researchers if submitted to a journal. It
is socially acceptable that a workshop paper will not have as much consolidation
as might be required of a journal article, since the criticism and evaluation of ideas
and models at a workshop are part of its purpose, but presenting a model with an
inadequate level of consolidation just wastes the other participants’ time.