Using temporal constraints to restrict search in a planner

O-Plan is an AI planner based on previous experience with the Nonlin planner and its derivatives. Nonlin and other similar planning systems had limited control architectures and were only partially successful at limiting their search spaces. O-Plan is a design and implementation of a more flexible system aimed at supporting planning research and development, opening up new planning methods and supporting strong search control heuristics. O-Plan takes an engineering approach to the construction of an efficient domain-independent planning system which includes a mixture of AI and numerical techniques from operations research. The main contributions of the work are centred around the control of search within the O-Plan planning framework, and this paper outlines the search control heuristics employed within the planner.