PHIGS and Part Hierarchies
In the next few chapters we will be discussing in greater detail both the object-oriented kernel system GEO++ and the graphics standard PHIGS (Programmer’s Hierarchical Interactive Graphics System). PHIGS is the graphics system that especially supports a part hierarchy by handling multi-level structures. Unfortunately, there is hardly any literature on PHIGS that allows an in-depth analysis of some of the problematic points available. Such an analysis is important, however, in order to master identified weak points by introducing object-oriented design principles. We do not wish to denigrate the work of those who defined PHIGS years ago by stressing these critical points. But developments in the field of interactive programming have since progressed. The object-oriented paradigm is gaining more and more ground and, as we shall see, almost necessarily and naturally calls for the revision of some basic principles of PHIGS.
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