In this paper, we present the results from a family of experiments conducted to assess whether the level of formality/precision in workflow modeling, based on UML activity diagrams, influences two aspects of construct comprehensibility: correctness of understanding and task completion time. In particular, we have considered two styles for workflow modeling with different levels of formality: a precise style (with specific rules and imposed constraints) and an ultra-light style (no rules, no imposed constraints). Experiments were conducted with 111 participants (Bachelor and Master students). In each experiment, participants accomplished comprehension tasks on two workflows, modeled either with the precise style or with a lighter variant. ...