Does object coupling really affect the understanding and modifying of OCL expressions?

Early and precise models started to play an increasingly relevant role since models themselves become the primary focus in recent initiatives of Model-Driven Engineering (such as Model-Driven Development and Model-Driven Architecture). However, a precise model cannot be obtained through the use of Unified Modeling Language (UML), due to the limited expressiveness of diagram-based UML notation. A textual add-on to the UML diagrams is needed, such as the Object Constraint Language (OCL), for reaching complete and consistent models and avoiding underspecification. Aware of the proliferation of measures for UML-based models and the lack of measures to capture the quality aspects of UML/OCL combined models we defined a set of measures for measuring the structural properties of OCL expressions. This paper carefully describes an experiment we have conducted to confirm the conclusions and strengthen the external validity of a previous family of experiments, with the purpose of investigating the relationship between object coupling in OCL expressions and the understandability and modifiability of OCL expressions. Empirical evidence that such a relationship exists is reaffirmed and consolidated.