We discuss external and internal graphical and linguistic representational systems. We argue that a cognitive theory of peoples' reasoning performance must account for (a) the logical equivalence of inferences expressed in graphical and linguistic form; and (b) the implementational differences that affect facility of inference. Our theory proposes that graphical representations limit abstraction and thereby aid processibility. We discuss the ideas of specificity and abstraction, and their cognitive relevance. Empirical support comes from tasks involving (i) the manipulation of external graphics; and (ii) no external graphics. For (i), we take Euler's Circles, provide a novel computational reconstruction, show how it captures abstractions, and contrast it with earlier construals, and with Mental Models' representations. We demonstrate equivalence of the graphical Euler system, and the non-graphical Mental Models system. For (ii), we discuss text comprehension, and the mental ...

The past decade has witnessed the emergence of an active visual programming research community.Yet, there has also been a noteworthy shortage of empirical evidence supporting the resulting research. This paper summarizes empirical data relevant to visual programming languages, both to show the current empirical status and to act as a call to arms for further empirical work.

Designers seeking to improve human-computer interfaces, particularly those concerned with programming environments, often assume that "graphics" will always result in an improvement over "text." Such claims are especially difficult to assess, given that people have used the terms "text" and "graphics" in different and conflicting ways throughout the literature.

Although great progress has been made in the development of visual languages, little attention has been paid to how diagrams in such languages should be entered into computers. This issue will have a great impact, however, on users' acceptance of visual languages. We present an analysis of the features of visual languages influencing diagram entry, and also the results of an experiment comparing users' performance on different types of diagram editors. This data is then used to suggest design guidelines for usable visual language front ends. 1: Introduction Visual notations for programs have been in existence virtually from the invention of programming, and visual languages that can be interpreted by computers have been in existence for the last 15-20 years. Since that time, the visual notations have become more complex as language designers have become more aware of the power of visual notations and as available technology has become more sophisticated. In contrast to these advances,...

GRASP is a software engineering tool which uniquely combines a source code diagramming technique, the control structure diagram (CSD), with other comprehension aids such as complexity visualization, syntax coloring and source code folding. The synergistic combination of these features in GRASP has the potential to be a powerful aid in any activity where source code is expected to be read. The primary focus of GRASP is to improve the comprehension efficiency of software and, as a result, improve reliability and reduce costs during design, implementation, testing, maintenance and reengineering. 1.1 Keywords Software visualization, folding, program understanding