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 OPlan planning framework, and this paper outlines the search control heuristics employed within the planner. These involve the use of condition typing, time and resource constraints and domain constraints to allow knowledge about an application domain to be used to prune the searc...

As realistic systems are built and commercial toolkits are created for planning and scheduling applications, it becomes increasingly important that modularisation of these "standard" components is attempted. This can lead to re-usability, embeddability and improved implementation provision. One early example of a standardised component is the Truth Criterion condition establishment algorithm which is now found at the heart of most activity based planning systems. The modularisation of this algorithm has led to an explosion of further development, empirical and theoretical study of this component. The provision of powerful constraint management languages and tools could lead to a rapid expansion of the benefits to be gained by identifying more standard components that can be combined and re-used in planning and scheduling systems. O-Plan2 is a command, planning and control architecture which has an open modular structure intended to allow experimentation on or replacement of various components. This paper describes the modular structure of the system along with the internal and external interface languages and protocols which are being developed on the O-Plan2 project. The research is seeking to isolate functionality that may be generally required in a number of applications and across a number of different planning, scheduling and control systems. This paper is intended to further discussions on the identification of suitable "standard" re-usable components in planning and scheduling systems.