Comments on "Formal specification of user interfaces: a comparison and evaluation of four axiomatic approaches" by U.H. Chi

A recent paper (see ibid., vol.11, no.8, p.671-88, Aug. 1985) compared several axiomatic methods of formal specification, one of which was Z. As a result of a comparison made with Z and a similar, but executable, specification language called Me too, it was pointed out that one of the Z specifications given was not correct. In this response, the erroneous function is described and some conclusions are drawn about the process of formal specification.<>