GKS in an object-oriented environment

Because of its basis properties, object-oriented programming is well suited to creating user interfaces or graphical applications. However, object-oriented systems are often without graphics or have only a graphical kernel which presents a very low level of use. Besides, such graphical kernels are dependent on the implementation. The use of graphical standards could be an alternative way to bring portability of the applications. Object-oriented systems are often implemented on top of Common Lisp or similar Lisp dialects. In this paper the implementation of an object-oriented shell of an available GKS implementation using an object-oriented extension of Common Lisp will be discussed.     

The GKS Input Model in Manifold

This paper describes the specification of the GKS input model in M anifold . The aim of the work reported in this paper was two-fold: first, to review the communication patterns implied by the GKS input model, and second, to evaluate the suitability of the M anifold language as a tool for defining complex dynamic interaction patterns that are common in non-trivial user interfaces.
The GKS input model is also adopted by all more recent ISO graphics standard documents. A more formal scrutiny of the inter-communication of the components of this model, excluding the implementation details of their functionality, is instructive in itself. It can reveal directions for improvement of its shortcomings and for generalization of its strengths for the ongoing effort to define the functionality of future graphics packages.
M anifold is a language for describing inter-process communications. Processes in M anifold communicate by means of buffered communication links called streams and by reacting to events raised asynchronously by other processes. Our experience shows that M anifold is a promising tool for describing systems of cooperating parallel processes. Our M anifold specification of the GKS input model offers a very flexible way to structure user defined logical input devices. Furthermore, it is simple and modular enough to allow easy extensions to include more functionality by local modifications. As such, it can serve as a basis for possible extensions and enhancements envisioned for future graphics packages.
1987 CR Categories: C.1.2, C.1.3, C.2.m, D.1.3, F.1.2, I.1.3, I.3.6, I.3.4.
1885 Mathematical Subject Classification: 68N99, 68Q10,68U05.     

A Multi-Microprocessor GKS Workstation

Implementers of graphical application sytems hesitate to interface their applications to the GKS standard not only because GKS functionality seems to be less suffcient for a particular application but also because the use of GKS-as it is offered in portable software implementions-uaually means a loss of system performance. This article describes an installation of GKS on a multi-microprocessor that is based on functional distribution principles as well as on the object-oriented distribution of a graphics system. The main concepts and advantages of a GKS workstation using more than one processing unit with at least one output pipeline are described. The flexibility of this approach opens a perspective view to a GKS workststion that is configurable to application requirements.     

GKS Programming in a PHIGS Environment

GKS is an international standard for the functional interface to 2D graphics, whilst PHIGS is currently an ISO work item for 2D and 3D graphics. In addition, PHIGS allows improved control over structuring graphics data in the system. With a new work item, the upwards compatability from GKS to PHIGS is being called into question. This paper is an attempt to give direction to these discussions by listing the implications of introducing a software layer between a GKS application program and a PHIGS environment on which this application is to be run. It is intended to highlight differences between the systems and to answer questions such as, “How compatible?”, “Is it possible?”, “How much does the software layer have to do?”, etc.     

A VLSI Support for GKS

This microprogrammed VLSI design places the GKS output functions on a single chip, leading the way to substantial enhancements in system performance.     

Implementing strings in Pascal

Sale¹ has proposed that strings be realized in Pascal using the existing sequence abstraction. This short note supports this proposal and shows how strings can be efficiently implemented in standard Pascal. The implementation is done in such a way as to leave existing programs undisturbed should strings be subsequently incorporated in the language and/or compiler.     

GKS certification—An overview

The rapid emergence of GKS implementations indicates the widespread acceptance of GKS as an international standard for computer graphics. It is essential however if the interests of the standard are to be preserved, that there be a feasible means of validating GKS implementations to ensure that adherence to the standard is maintained. This paper describes an overall methodology for GKS certification, and outlines in more detail the validation of data returned by GKS to an application program. Validation of output generated by GKS is discussed in general terms in this paper, and in more detail in other papers in this issue.     

3D extension to GKS

The Graphical Kernel System GKS has [1] been established as the first standard in the field of Computer Graphics covering two-dimensional (2D) graphics. Now work is going on to develop standards in related areas. One important effort is the extension of GKS for three-dimensional (3D) graphics. This paper will briefly overview the history of standardization efforts with respect to 3D graphics and then report the current activities of various national and international standardization bodies for extending GKS to 3D. Then the paper will concentrate on GKS-3D [2], a proposal for a 3D extension of GKS which is developed by the Dutch standardization committee NNI in close collaboration with the International Organization for Standardization ISO/TC97/SC21/WG2. Technical work is expected to finish in 1985. Scope and purpose of this future 3D standard and goals of the design are given and the functionality of the 3D extension is described in some detail. As technical work on GKS-3D is going on, changes may occur to the standard document. The major issues will be surveyed and trends will be sketched.     

On publication Pascal

Having recently read several new Pascal textbooks, I was struck by the multitude of ways in which programs are represented in print. Some of these are more pleasing to the eye than others, and with a typesetting machine, anything is possible. However, several books are being produced these days from typewritten copy and there seems to be no accepted second-best to the italics-and-bold favoured by most publishers. It would also be desirable if the style used by books could correspond more closely to that which is handwritten or computer-produced. This note summarizes the possibilities and makes a call for stability, if not outright standardization.     

Pointer variables in concurrent Pascal

Concurrent Pascal and similar languages are inefficient when used to program systems where processes exchange large messages. The inefficiencies, caused by copying of data, can be removed by introducing pointer variables, and this paper shows how this is done without allowing unrestricted sharing of variables. Pointer variables also give means to solve problems of dynamic resource allocation and dynamic addressing. Examples with performance figures for an actual implementation are given.