Projects Overview Encyclopedia Project (Explanations) ## Assessment: Global modelling perspective## Encyclopedia of World Problems and Human Potential1. Modelling based on equations
Global or world modelling may be understood as the attempt to represent rigorously the economic, political, social, demographic and/or ecological issues and their interdependencies on a global scale. The models map these relationships as explicit mathematical equations which may be "run" forward in time to study their dynamic behaviour. They can thus be used to simulate future developments under a variety of conditions. Such modelling may be considered as the most sophisticated approach to dealing systematically with the nature of, and solution to, world problems. Global modelling is seen by some as the key to understanding the global
problematique. Indeed it was the group that initiated this approach that
first formulated the term "global problematique". The accomplishments of
this group through the 1970s have been reviewed, by some of those involved,
in an exceptionally honest book: The authors distinguish two types of model: (a) mental or verbal models; and (b) mathematical or computer models (which may be based on mental models). Mental models are complex, shifting and often unverbalized, and when they are verbalized can be understood as implying different mental models from those intended. Computer models express precise mathematical relationships such that conclusions can be calculated from initial assumptions, especially when the situation is so complex that it cannot be encompassed in words or simple equations. The authors perceive such computer models as providing the necessary guidance for policy decisions in response to the global problematique. Some may even perceive such guidance to be both necessary and sufficient. Global modelling has continued to proliferate in the 1980s, both geographically and in terms of issues and methodologies. An overview of global modelling in 1985 was provided for UNESCO by Heinrich Siegmann of the Wissenschaftszentrum Berlin (UNESCO, 1987). Some 29 models were then considered relevant to the study. Global modelling is considered to be still developing as a research field. According to Siegmann, hardly any model should be considered completed. The global models represent the confluence of modelling streams from three disciplines: political science, systems dynamics and econometrics. Global economic models have been put to use by policy-making institutions in order to aid in short-to-medium term projections. The modelling time horizon has in general become shorter. The issues addressed have become more specific. Modellers regretted the cessation in 1981 of the Global Modelling Conference sponsored by the International Institute for Applied Systems Analysis. The conference had provided a consolidating infrastructure for global modelling, a role which UNESCO considered providing prior to its own programming and budgetary difficulties from 1987.
Following the appropriation of the term "global modelling" by those designing models based on mathematical equations, it might be assumed that no other forms of "modelling" of the global problematique are possible. Mental and verbal models are less satisfactory for the reasons noted above, but interesting models of systems can also be explored using analog methods. It is interesting to note that a number of disciplines use other kinds of models in order to grasp the nature of complex systems. In the case of chemistry, molecular structures made up of many thousands of atoms are displayed graphically under conditions where the real complexities of the system do not lend themselves to mathematical analysis. This example points to a key issue, namely availability and adequacy of information in constructing equation-based models. For such an equation to be formulated, precise information must be available through which a mathematical function can be defined. If the information cannot be formulated in precise terms, then nothing can be incorporated into the model. Unfortunately, very few non-economic problems can be formulated in precise terms. It is, however, possible to use a different kind of precise mathematical relationship to provide some means of reflecting fuzzy perceptions. A network of perceived relationships between problems can be progressively identified. Such a network model can be held and explored on computer (see Section TZ). Such global modelling is based on graph theory (and related disciplines), a quite distinct branch of mathematics. It has, for example, been used in artificial intelligence research to model (and interrogate) systems of attitudes held by an individual.
Global modellers have not envisaged this possibility, which is the inspiration behind the project of which this Encyclopedia is a product. It is important to recognize the fundamental difference between these two approaches: - assumptions concerning the objectivity of the "real world" vs. assumptions that "subjective" and "erroneous" assessments of "facts" and attitudes may be just as real to some constituencies and, as such, may have real consequences;
- dependence on quantitative ("hard") data vs. registration of qualitative ("soft") data;
- insights only emerge from mathematical analysis vs. insights emerge from relative positioning of nodes in a network;
- complexity can only be managed to the extent that it can be reflected in a set of equations vs. complexity can be navigated (in the same way that a complex road map is navigated);
- data sets must be reliable and complete to be of any value vs. recognition that data sets are necessarily partial and unreliable.
- the structure of the model does not involve an on-going dialogue with the constituencies whose views are represented there vs. the model is only useful to the extent that it reflects the current, and potential, biases of the views reflected therein.
From the perspective of conventional global modellers, the kind of information collected for this Encyclopedia is completely superficial since it does not analyze the relationship between economic and social factors and express them in mathematical terms so as to define a model which can be explored under different conditions. There are a number of weaknesses in this position to which this project provides a partial response.
Models now tend to have boundaries that are more narrowly defined, and
to have shorter term horizons and more disaggregation (
On the depth versus breadth of a model Seigmann's notes:
Again it is interesting that there appears to be no recognition by such modellers that the status of a model needs to be reflected in the model itself. In the above quotations the model is treated as the product of an interest group seeking to impose its perspective. The model fails to encode the dynamics relating its perspective to others, whether other modellers, other disciplines, or the wider public. By contrast, in the case of the project giving rise to this Encyclopedia, the dilemma created by conflicting perspectives is central to the whole approach. It is assumed that yet another formulation of "the truth" or "the methodology" would be as significant as the multiplicity of other such extant "answers" to the challenge of the times. The task is therefore defined as one of providing an appropriate framework through which conflicting and incommensurable answers and (perceptions of) "facts" can be related, at least to some degree. At the data and analytic level, graph and network theory is seen as providing a way forward where more rigorous, and possibly over-demanding techniques cannot travel. In terms of comprehension of more complex dynamics and patterns by wider public, the role of metaphors has been emphasized. Given the current advances in graphic software techniques, there is no reason why these two approaches should not be "married" in some way that would be of immediate significance to policy-making. Organized in this way, specific equation-based models could be integrated as required.
In a follow up for UNESCO of the Seigmann study, Sam Cole (1987) concludes
that conventional |

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