Transforming and Refining Abstract Constraint Specifications

To use constraint technology to solve a problem, the solutions to the problem must first be characterised, or modelled, by a set of constraints that they must satisfy. A significant part of the modelling process can be characterised as refinement, the process of generating a concrete model from an abstract specification of the problem. Expert modellers also identify and perform transformations that can dramatically reduce the effort needed to solve the problem by systematic search. Through a case study of modelling a simplified version of the SONET fibre-optic communication problem, this paper examines the processes of refinement and transformation, and especially the interaction between the two.