VDM and Z: A comparative case study

The specification notations of VDM and Z are closely related. They both use model-based specification techniques and share a large part of their mathematical notation. However, the approaches taken to writing specifications differ in other, more subtle, ways.We present a comparative case study of VDM and Z for specifying database systems. John Fitzgerald and Cliff Jones in their paper entitled “Modularising the formal description of a database system” in the proceedings ofVDM '90: VDM and Z (LNCS Vol. 428, Springer-Verlag) provide the basis for the comparison. We present equivalent Z specifications to the VDM specifications contained in their paper.The approach taken in writing the Z specifications is to reuse as much as possible of the Z mathematical toolkit and to build the system specification from specifications of components of the system.In their paper, Fitzgerald and Jones emphasise their modularisation facilities. While the facilities for modularisation in Z are not as powerful, they are adequate for the specification of the database systems presented.