DISSPLA(ID:5662/dis009)Interactive graphics programming language References: in Douglas Lewin (Ed) Interactive Systems (1975), Online, Uxbridge, England. view details INTRODUCTION Social scientists are a large group of potential users of computer graphics. They make heavy use of computers in both research and teaching. When they use computers they are accustomed to sophisticated software and unsophisticated devices. They rarely write special purpose programs and only a small subset use special hardware. Instead, they rely on high quality, multipurpose-software packages of canned programs. These and other characteristics have implications for the design of graphics software and hardware. These potential users will expect graphic software to be easy to use, powerful, inexpensive and device independent. If computer graphics evolves in these directions social scientists will become major consumers. Computer graphics can aid the social scientist who is involved in data analysis in two distinct ways. First, computer graphic displays can be used after the research process to communicate research results to others in publications, in presentations and in teaching. This use requires that graphs be clearly labelled and adjustable in format. Second, computer graphics can be used during the research process to communicate results to the primary researcher. This can be accomplished by embedding the graphics within data analysis software. This use requires that the graphics be obtained easily in addition to the traditional printout of results; ease of use is more important than flexibility of format or elegance of labelling. We have developed graphic software to satisfy the perceived basic needs and expectations of the social scientists and which have been well received and utilized at the University of Michigan. It is embedded in the interactive statistical system, MIDAS,[1] and appears as a stand alone interactive prompter, GRAPH.[2] In the future this software may be available more generally over a national computer network. Our graphic software includes a set of modules which correspond to the visual components of a display, such as an axis with tic marks and labels or a legend. This modularity provides extensibility of the set of available displays with minimal effort. Our software in turn employs the University of Michigan Integrated Graphics library [3] to define a visual component as a set of device-independent lines or text strings. The Integrated Graphics routines handle all graphic device communications including that for storage tube terminals and the CalComp ploter. We are not attempting in this paper to describe the internal design of the software we have produced. Our purpose is to describe the social science computing environment and the external form of the graphic software designed both to fit that environment and to introduce social scientists to computer graphics. in Proceedings of the 3rd annual conference on Computer graphics and interactive techniques, July 14-16, 1976, Philadelphia, Pennsylvania view details Historically SKETCHPAD (Sutherland) was the first widely recognized general purpose graphics system. The SKETCHPAD system consists of a collection of subroutines called interactively through a menu selection process. The system allows pictures to be constructed hierarchically from other pictures and is noted for its use of a ring data structure to store picture descriptions. Kulsrud, Williams, and Giloi presented models for the definition of a general purpose graphics language, Kulsrud suggested that the first version of the proposed language have written commands and that it later be adjusted to accept input from graphics devices such as light pens and trackballs. The language she described was capable of picture description, manipulation, and analysis. Although it could be used with interactive applications programs, it was not an interactive language. Williams described a language that provided (i) data types with related operations particularly suited to graphical applications, and (2) the ability to add new data types and operations. For example, a "point,' could be a data type, and a specially defined addition operator would operate on that data type. The language was thus highly extensible, but it was not interactive. Giloi proposed a model to be used in constructing either subroutine packages for graphic display applications or graphical extensions to existing languages. In this model, pictures were described as a hierarchy of subpictures and picture primitives. Primitives were defined as anything for which there was a hardware generator in the display processor, placing limits on the device independence of a language developed from his model. An interactive version of the model was developed by extending APL to include graphics capabilities, and a non-interactive version was developed as a FORTRAN subroutine package. The general purpose graphics systems presented in recent years can be classified as (i) subroutine packages for graphics applications, (2) graphics extensions to existing languages, and (3) new languages possessing graphics capabilities. Graphics subroutine packages are most widely distributed particularly by manufacturers of graphics display hardware. Some example packages are GINO-F, GPGS, GRAF, DISSPLA, and EXPLOR. Most packages are limited to the manipulation of picture displays with few programming control or storage capabilities. Where such abilities are available they often serve specialized purposes as in WAVE, a package for waveform analysis. One exception is the VIP system where the user is able to combine the available system function subroutines into special purpose functions which can then be used in the same way that the original system functions were used. Extensions of an existing language such as Euler-G, IMAGE, APLBAGS, APLG, and PENCIL, provide a programmer with graphics capabilities as well as general programming features. Euler-G has excellent data structure definition facilities. IMAGE, an extension of FORTRAN, cannot provide the data structure description capabilities that are available in Euler-G, but it has the advantage of being based on the most widely distributed host language available. APLBAGS, APLG, and PENCIL, an extension of the MULTILANG on-line programming system, are truly conversational languages. GRASP, a PL/I extension, is a compiled language but it allows dynamic interaction. GRASP also allows the definition of models from which complex pictures can be created hierarchically. ESP3, an extension of SNOBOL4, is a non-interactive language from which many of the high-level concepts found in PIGLI are drawn. Language extensions are found mainly in experimental installations. Two complete graphics languages are METAVISU and GLIDE. Both take characteristics from a base language (PL/I and ALGOL, respectively) and add capabilities for defining, displaying, and manipulating pictures. Full languages are less widely distributed than subroutine packages or language extensions. in Proceedings of the 1978 annual conference 1978, Washington, D.C., United States view details |