The following article has been submitted to the present ETAI area.   Austin Tate: Representing Plans as a Set of Constraints - the <I-N-OVA> Model. Abstract: his paper presents an approach to representing and manipulating plans based on a model of plans as a set of constraints. The I-N-OVA ( Issues - Nodes - Orderings/Variables/Auxiliary) model is used to characterise the plan representation used within O-Plan and to relate this work to emerging formal analyses of plans and planning. This synergy of practical and formal approaches can stretch the formal methods to cover realistic plan representations, as needed for real problem solving, and can improve the analysis that is possible for production planning systems. I-N-OVA is intended to act as a bridge to improve dialogue between a number of communities working on formal planning theories, practical planning systems and systems engineering process management methodologies. It is intended to support new work on automatic manipulation of plans, human communication about plans, principled and reliable acquisition of plan information, and formal reasoning about plans.