Using Verbal Protocols to Assess the Influence of Import-Coupling on the Comprehensibility of OCL Expressions

The import coupling of an object constraint language (OCL) expression increases when the expression operates within a large context of a Unified Modelling Language (UML) model. The expression would thus exhibit a decrease in its comprehensibility, and in consequence, the maintainability of the OCL expressions could be affected, due to the fact that modelers need to know all the artifacts upon which the expression relies. In order to explain the cognitive complexity of modelers dealing with OCL expressions with high import- coupling we have carried out a think aloud experiment which is described in detail in this paper. The experiment is part of a project which we are developing with the goal of obtaining valid measures through which to assess the influence of import coupling on OCL expression maintainability. The empirical results show evidence that: (1) reified objects, problem objects and their relationships constitute the main components of the cognitive complexity of modelers; (2) modelers use different cognitive approaches to comprehend an OCL expression within a UML/OCL model.