Models are created by people and people make mistakes. For this reason, it is necessary to validate both the contents and the utility of a model. As has been noted in previous chapters, models should be complete, correct, and concise to be effective. Accuracy and completeness are necessary attributes of a correct model, whereas utility and maintainability are attributes of an effective model. To ensure that a model has these attributes, a thorough review and verification procedure should be conducted. There are at least four good techniques to validate a model: team reviews, simulation, testing, and direct application.