The representation, for a variety of purposes, of a system seen, calculated or experienced in one dimension in another dimension or medium. It can be simple like a diagram, a physical model, a picture, a complex like a set of calculus equations, or a computer program. Its uses include investigation, theorizing, and fitting theories to the world. A conceptual model is a theoretical representation of a system, for example a set of concepts, their relationships and equations to describe the workings of the atmosphere for the purpose of weather forecasting. A mathematical model is a description of a system using mathematical concepts and language and can be used in the natural sciences and engineering disciplines, as well as in non-physical systems such as the social sciences. An economic model is a construct representing economic processes by a set of variables, exogenous and internal and a set of logical and/or quantitative relationships between them. Opagio models business processes. It is unique in that the variables describing the processes are empirical representations of the actual working of the organisation, and the performance measurement variables replicate as total factor efficiency those used to calculate total factor productivity in the economy.