Duce, D. A.2015-10-052015-10-0519891017-4656https://doi.org/10.2312/egtp.19891020There are now three International Standards for application program interfaces for computer graphics programming, GKS, GKS-3D and PHIGS. In this paper a simplified model GKS-like system is described and a 2D PHIGS-like system is then described in terms of this and a centralized structure store. Formal specifications of the systems are given illustrating how the specification of a system can be built up from a hierarchy of simple components. The purpose of the paper is to illustrate one approach to the description of a compatible family of graphics standards and the use of formal specification techniques in this process.10.2312/egtp.19891020