This chapter considers the use of specifications such as information models as the basis for implementations. Where the models are at a conceptual level, direct mapping to implementations such as databases is unlikely to produce optimum results. The chapter discusses the use of model transformations as a way of converting conceptual models to implementation models. It also introduces an informal categorisation scheme for transformations. Examples are used throughout. These are based on the EXPRESS information modeling language that has been defined as part of ISO 10303. Finally, a brief description of the STEPWISE model transformation environment is presented.