Qualitative Decision Support using Prioritised Soft Constraints

A key assumption of all problem-solving approaches based on utility theory is that we can assign a utility or cost to each state. This in turn requires that all criteria of interest can be reduced to a common ratio scale. However, many realworld problems are difficult or impossible to formulate in terms of minimising a single criterion, and it is often more natural to express problem requirements in terms of a set of constraints which a solution should satisfy. In this paper, we present a decision support system for route planning in complex terrains based on a novel constraint-based search procedure, A with bounded costs (ABC), which searches for a solution which best satisfies a set of prioritised soft constraints, and illustrate the operation of the system in a simple route planning problem. Our approach provides a means of more clearly specifying problem-solving tasks and more precisely evaluating the resulting solutions as a basis for action.