The point of reference for this paper is the theoretical structure of disaggregated, general equilibrium models of the ORANI type, as outlined in Dixon et al. (1982) and Vincent (1981). This theoretical structure has been applied in a variety of contexts, with particular models differing widely, depending on data availability and the purpose at hand. However, all applications use some subset of the theoretical structure described by Dixon et al. and Vincent. These references are therefore taken as benchmarks, from a theoretical viewpoint.