Current interactive user interface construction tools are often more of a hindrance than a benefit during the early stages of user interface design. These tools take too much time to use and force designers to specify more of the design details than they wish at this early stage. Most interface designers, especially those who have a background in graphic design, prefer to sketch early interface ideas on paper or on a whiteboard. We are developing an interactive tool called SILK that allows designers to quickly sketch an interface using an electronic pad and stylus. SILK preserves the important properties of pencil and paper: a rough drawing can be produced very quickly and the medium is very flexible. However, unlike a paper sketch, this electronic sketch is interactive and can easily be modified. In addition, our system allows designers to examine, annotate, and edit a complete history of the design. When the designer is satisfied with this early prototype, SILK can transform the sket...

There is widespread anecdotal evidence that expert programmers make use of visual mental images when they are designing programs. This evidence is used to justify the use of diagrams and visual programming languages during software design. This paper reports the results of two studies. In the first, expert programmers were directly questioned regarding the nature of their mental representations while they were engaged in a design task. This investigative technique was used with the explicit intention of eliciting introspective reports of mental imagery. In the second, users of a visual programming language responded to a questionnaire in which they were asked about cognitive processes. The resulting transcripts displayed a considerable number of common elements. These suggest that software design shares many characteristics of more concrete design disciplines. The reports from participants in the two studies, together with previous research into imagery use, indicate potential...

The Cognitive Dimensions of Notations framework has been created to assist the designers of notational systems and information artifacts to evaluate their designs with respect to the impact that they will have on the users of those designs. The framework emphasizes the design choices available to such designers, including characterization of the user's activity, and the inevitable tradeoffs that will occur between potential design options. The resulting framework has been under development for over 10 years, and now has an active community of researchers devoted to it. This paper first introduces Cognitive Dimensions. It then summarizes the current activity, especially the results of a one-day workshop devoted to Cognitive Dimensions in December 2000, and reviews the ways in which it applies to the field of Cognitive Technology.

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Modern computer systems routinely present information to the user as a combination of text and diagrammatic images, described as "graphical user interfaces". Practitioners and researchers in Human-Computer Interaction (HCI) generally believe that the value of these diagrammatic representations is derived from metaphorical reasoning; they communicate abstract information by depicting a physical situation from which the abstractions can be inferred. This assumption has been prevalent in HCI research for over 20 years, but has seldom been tested experimentally. This thesis analyses the reasons why diagrams are believed to assist with abstract reasoning. It then presents the results of a series of experiments testing the contribution of metaphor to comprehension, problem solving, explanation and memory tasks carried out using a range of different diagrams. The results indicate that explicit metaphors provide surprisingly little benefit for cognitive tasks using diagrams as an external re...

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.

Abstract. This paper explores a concept of sketch-based informal user interface for graphic computing, which can be characterized by two properties: strokebased input and perceptual processing of strokes. A sketch-based graphics input prototype system designed for creative brainstorming in conceptual design is introduced. Two core technologies for implementing such a system, adaptive sketch recognition and dynamic user modeling, are also outlined. 1

In this paper Green's (1989) notion of "cognitive dimensions" is used to consider the properties of notations and media for sketching. First, a cultural-cognitive approach to HCI research is briefly outlined which draws on some ideas from "distributed cognition" and Russian psychology. Rather than focussing on the cognitive aspects of an activity or the social aspects (as do cognitive psychology and ethnography, respectively) this approach attempts to describe the artifacts used in an activity in a cognitively and socially relevant way. It is argued that such an approach requires a framework within which to analyse external representations, and that Green's "cognitive dimensions" provide such a framework. The cognitive dimensions framework is described and then used to interpret a study of collaborative idea sketching which used interviewing, observational methods and a questionnaire survey of 128 academics. This analysis resulted in a cohesive and comprehensive characterisati...

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