Generation of Graphical User Interfaces (GUIs) from Business Process Model Notation (BPMN) models is a step manually performed by an analyst in any information system development. By analyzing twelve BPMN projects and comparing them with their associated GUIs, a set of rules for mapping BPMN models expressed in terms of BPMN patterns to GUIs has been identified. This paper provides three main contributions: an empirical validation of these mapping rules; a classification of their alternatives to identify which ones support usability; and the validation of this classification. We conducted an experiment to study whether 43 participants apply the same rules as previously identified with response variables as: correctness of the rules, their completeness, perceived usefulness and intention to use. To select the mapping rules alternatives that effectively impact usability, we classified them according to empirically validated usability guidelines found in the literature. We also validated them with participants and response variables as: correctness of the guidelines, their perceived usefulness and intention to use. Correctness of the mapping rules was assessed positively (74%), as well as their completeness (76%), perceived usefulness (95%) and intention to use (68%). Correctness of the usability recommendations for using these mapping rules was also assesses positively (57%), as well as their perceived usefulness (86%) and intention to use (72%). This paper provides analysts with effective and efficient guidance on how to apply them consistently and to feed a software for semi-automatic transformation of BPMN models into their corresponding GUIs.