Comparing comprehensibility of modelling languages for specifying behavioural requirements

The selection of a suitable modelling language influences the success of software modelling. Several experiments comparing the comprehensibility of graphical modelling languages have been published. However, no published study comparing the comprehensibility of functional requirements modelled in different graphical modelling languages exists. This paper evaluates how two requirements modelled in a sequence-based notation, Modal Sequence Diagrams, and in a state-based notation, Timed Automata, compare with respect to comprehensibility. A controlled experiment with 22 student from an undergraduate course on software modelling was performed. Our results show no significant differences with respect to the comprehensibility of the two different languages, but subjects who answered the questionnaire for the sequence-based notation completed significantly more answers in the given time limit. These initial results indicate that choosing a modelling language for requirements modelling based on convenience does not significantly affect the understanding of the resulting requirements.