Global view Optimizing a multi-process view of manufacturing can bring economies that are not apparent if each part of the plant is considered separately. For instance, past work we have done on the choice of spare parts inventory for a set of complex equipment makes it clear that, if parts can be cannibalized between equipment, and some parts are important but rarely needed, then a smaller stock of parts can adequately provide for more equipment. It is only through a global view of the plant that one can see the value of each part insuring against failures in multiple processes, and the value of choosing for those processes equipment that uses the same parts. Similarly, as well as parts, equipment and personnel may be able to cover multiple contingencies: for instance, if there is some process that must be kept running at the expense of others, the global view can reveal the benefits of manning the less important processes with equipment and personnel that can be shifted to the critical process if necessary. So, it is worth modeling the whole plant as a system because great gains in efficiency and robustness can be made, reducing complexity and increasing flexibility.

Solution The model of the plant involves many components that can be chosen and combined in various ways to form the plant's design. With computer assistance, many combinations of these components – plant designs, or subsets thereof – can be generated and evaluated, their performance being determined through stochastic models with reference to the scenarios that are of the most interest or concern. The costs that are calculated for each design must include set-up costs (whether from scratch, or from the existing plant design), running costs, and safety risks. Typically, those costs must be traded off against each other, and against the plant's performance in the context of various situations. We enable the decision-maker to navigate the tradeoffs among costs and benefits, finding the best way to streamline their plant.