There are a plethora of system development methods available to practitioners, all purporting to be the best method. This variety brings with it an element of choice which can be perceived as a problem in itself, quite apart from the issue of developing a system. This paper uses elements of the ontological framework of Bunge, Wand and Weber to critically examine the constructs of several methods used to develop requirements specifications (and, in particular, business process models), notably the Business Rules Diagram (BRD) Method and the Unified Modelling Language (UML).