The use of Ockham's Razor in object-oriented modeling

From the perspective of a practitioner, the development of perfect equation-based models is limited by language, hardware, and one's own mind. While the first two aspects are covered extensively in literature, only little attention has been given to the third one. We make a case for simple models, with a focus on two aspects: use of inheritance and creation of flexible models. Both can have adverse side-effects if used without restriction. To exemplify this discussion, two versions of a library as used in the aerospace industry are compared. The old version made heavy use of inheritance and tried to conduct everything with a minimal number of components. It was completely redesigned after maintenance efforts became too high. A psychological experiment was performed, where the effect of inheritance on the ability of participants to understand a model was analyzed. Results showed that each level of hierarchy significantly increases the time to understand a model by 26.65 s, when correcting for total model length. This supports our hypothesis that flat models are easier to understand than deeply nested models.