Analysing Modes and Subtypes in Z Specifications

Poor requirements are the cause of a large proportion of defects in released software. Requirements can be improved by using mathematical modelling techniques. These have a number of advantages and a singlemajor disadvantage–it is difficult to demonstrate a formal specification to a client or user. One proposed solution to this problem is to automatically derive (executable) prototypes of a system from a formal specification by using analysis. This process is known as animation. In this report we focus on the analyses used in an animation tool for the specification language Z. Specifically, we look at mode and subtype analyses. More extensive motivation and discussion of other aspects of the tool can be found elsewhere.