  Organisations, whether in government, industry or commerce, are required to
make decisions in a complex and uncertain environment. The way models are used
is intimately connected to the way organisations make decisions and the context
in which they make them. Typically, in a complex organisation, multiple related
models will often be used in support of a decision. For example, engineering
models might be combined with financial models and macro-economic models in
order to decide whether to invest in new production capability. Different parts
of a complex organisation might operate their own related models which might
then be presented to a central decision maker. Yet in practice, there is little
awareness of the practical challenges of using models in a robust way to
support decision making. There is significant scope to improve decision making
though an enhanced understanding of the role and limitations of modelling and
through the application of cutting edge methodologies and organisational best
practice. This report is in the form of a 'white paper', whose purpose is to
identify key issues for consideration whist postulating tentative approaches to
these issues that might be worthy of further exploration, focussing on both
technical and organisational aspects. It begins with a framework for
consideration of how model-based decisions are made in organisations. It then
looks more closely at the questions of uncertainty and multiple models. It then
postulates some technical statistical and organisational approaches for
managing some of these issues. Finally, it considers the way forward, and the
possible focus for further work.
