Measuring Object Coupling in OCL Expressions: A Cognitive Theory-Based Approach

Coupling is considered one of the most complex software quality attributes in object oriented (OO) systems. We belief that OCL expressions provide essential coupling information at early phases of software development. For that reason, we started to study if object coupling information obtained from OCL expressions affects the quality of the model that is finally delivered, based on the hypothesis that object coupling (an structural property) of an OCL expression within a UML/OCL model (artifacts) can influence on the cognitive complexity of modelers (subjects), and high cognitive complexity leads to OCL expressions exhibit undesirable external qualities, such as reduced comprehensibility and modifiability. In this paper we explain the influence of object coupling on the comprehensibility and modifiability of OCL expressions following a cognitive theory-based approach. We study cognitive complexity using mental and cognitive models to explain the rationale of the measures we defined for measuring object coupling. This cognitive theory-based approach was also used for obtaining a clear explanation of a family of experiments we run to confirm our hypothesis. The empirical results reveal that there is empirical evidence that object coupling is strongly correlated with the comprehensibility and modifiability of OCL expressions