Many people are dependent on desktop end user tools such as spreadsheets and databases to manage their data. While they may have the technical skills to set up data repositories, many end users lack the analysis skills to design data models which reflect their often deceptively complex requirements. We advocate that a comprehensive data model should always be developed, with expert help, so that the end user can feel confident the subtleties of the data are fully understood. We then suggest that some pragmatic decisions can be made to simplify the model so that the end user can retain control over setting up and maintaining the application.