An empirical investigation of the comprehensibility of requirements specifications

It is a commonly held view by software engineers that informal requirements specifications are easier to comprehend than formal requirements specifications. Moreover, the training time required to gain a sufficient level of understanding informal notations is unknown. This paper presents an empirical study carried out to compare the comprehensibility of two specifications, a formal specification and an informal (or semi-formal) specification, in an attempt to quantify the amount of training needed to understand formal methods. The two specifications used implemented the same logic, namely a portion of the Irish Electoral System. The "informal" specification was taken directly from the legal definition of the count rules for Irish elections, and the formal specification was an implementation of the same in CafeOBJ. Both Quantitative and Qualitative data was collected. Although participants had received twenty-five hours training in formal methods, the results show that the informal specification was more comprehendible than the formal specification.