Since the mid eighties educational concepts based on students’ work as organized in groups and based on project work with assignments from the real world have dominated Danish engineering programmes as well as many others and proved valuable in terms of preparing the students for complex working situations. The Qualification Frame terminology with emphasis on competencies pushes in the same direction. In the definition of didactical methods it is suggested that theory to a large extent be substantiated by examples from the professional field in question, and that the project work comprises a range of disciplines to appear realistic. With changing and more varying job profiles it may be a threat that students are pushed to achieve results at the expense of the supporting theory or performing sensitivity analyses. This first inspired me to look more closely into the students approach to and qualifications in theoretical subjects. Subsequently it appeared rewarding to set up a tool describing a systematic approach to the application of theory and performing sensitivity analyses, as a supplement to achieving results in a project, or building/ constructing something as the “I” and “O” in the CDIO terminology suggest. Engineers are very familiar with working with models, be it physical or theoretical. Proper application of the traditional modelling concept leads the students through the same stages as physically making a product, and hence enlarging the concepts of implementing and operating.