Assessing the Effect of Screen Mockups on the Comprehension of Functional Requirements

Over the last few years, the software engineering community has proposed a number of modeling methods to represent functional requirements. Among them, use cases are recognized as an easy to use and intuitive way to capture and define such requirements. Screen mockups (also called user-interface sketches or user interface-mockups) have been proposed as a complement to use cases to improve the comprehension of functional requirements. In this paper, we aim at quantifying the benefits achievable by augmenting use cases with screen mockups in the comprehension of functional requirements with respect to effectiveness, effort, and efficiency. For this purpose, we conducted a family of four controlled experiments, involving 139 participants having different profiles. The experiments involved comprehension tasks performed on the requirements documents of two desktop applications. Independently from the participants’ profile, we found a statistically significant large effect of the presence of screen mockups on both comprehension effectiveness and comprehension task efficiency. While no significant effect was observed on the effort to complete tasks. The main “take away” lesson is that screen mockups are able to almost double the efficiency of comprehension tasks.