Experiences in Using the Abstract Machine Notation in a GKS Case Study

This paper discusses the authors' experiences in re-engineering and subsequently refining part of a Z-style specification of the Graphics Kernel System using the Abstract Machine Notation as supported in the B Toolkit. 1 I n t r o d u c t i o n "B User Trials" is a collaborative project between Lloyd's Register, Rutherford Appleton Laboratory, Program Validation Limited and the Royal Military College of Science with the aim of subjecting the B Abstract Machine approach [Ab94] to industrial usage. The project encompasses four case studies with the aim of exposing the method and tools to a range of technical problems drawn from both industrial and research sources, e.g. [BR93]. It is also developing training courses in B technology [HH94] and proposing methodological extensions, [LH94], [BM94]. This paper reports on the experience of the application of the B Toolkit to specification and refinement of (part of) the draft GKS standard [ISO93]. This study investigates the use of abstract machines in specifying a system which contains a large amount of repetition. The starting point is the draft GKS specification. This is given in a Z style, with the intention that the initial abstract machine specification should bear close resemblance to this specification; thus we do not allow ourselves a carte blanche approach, so that we must investigate how well B adapts to "cohabiting" with another notation. Another area of interest lies in building and checking a formal relationship between the specifications of GKS operations and sets of programming-language bindings for them, in the hope that B's refinement and implementation techniques and the B Toolkit's support will yield useful insights. A wide variety of specification techniques, including VDM, Z, OBJ and LOTOS, have been applied to aspects of GKS; for example, see [ND94], [DD92], [DP91] and [DF87]. The work reported on here has concentrated on a number of experiments in specification style derived from the application, with the aim of * This work was supported by the UK DTI/SERC project "B User Trials" (IED4/1/2182).