The cognitive dimensions framework is a broad-brush evaluation technique for interactive devices and for non-interactive notations. It sets out a small vocabulary of terms designed to capture the cognitively-relevant aspects of structure, and shows how they can be traded off against each other. The purpose of this paper is to propose the framework as an evaluation technique for visual programming environments. We apply it to two commercially-available dataflow languages (with further examples from other systems) and conclude that it is effective and insightful; other HCI-based evaluation techniques focus on different aspects and would make good complements. Insofar as the examples we used are representative, current VPLs are successful in achieving a good `closeness of match', but designers need to consider the `viscosity' (resistance to local change) and the `secondary notation' (possibility of conveying extra meaning by choice of layout, colour, etc.).

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.

A programming system is the user interface between the programmer and the computer. Programming is a notoriously difficult activity, and some of this difficulty can be attributed to the user interface as opposed to other factors. Historically, the designs of programming languages and tools have not emphasized usability. This paper describes the process we used to design HANDS, a new programming system for children that focuses on usability, where HCI knowledge, principles, and methods guided all design decisions. The features of HANDS are presented along with their motivations from prior empirical research on programmers and new studies conducted by the authors. HANDS is an event-based language that features a concrete model for computation, provides operators that match the

Large software projects often require a programmer to make changes to unfamiliar source code. This paper presents the results of a formative observational study of seven professional programmers who use a conventional development environment to update an unfamiliar implementation of a commonly known video game. We describe several usability problems they experience, including keeping oriented in the program’s source text, maintaining the number and layout of open text documents and relying heavily on textual search for navigation. To reduce the cost of transferring knowledge about the program among developers, we propose the idea of wear-based filtering, a combination of computational wear and social filtering. The development environment collects interaction information, as with computational wear, and uses that information to direct the attention of subsequent users, as with social filtering. We present sketches of new visualizations that use wear-based filtering and demonstrate the feasibility of our approach with data drawn from our study.

This paper proposes a new programming language and environment for children. This system will be designed to be easy to learn and use, without sacrificing the power necessary to create sophisticated programs that rival commercial software such as games and simulations. Throughout the design and refinement of this system, I will apply prior results from empirical studies of programmers and the psychology of programming, my own empirical studies about the ways that nonprogrammers naturally express solutions to programming tasks, and usability testing.

External representations (ERs) are effective in reasoning due to their cognitive and semantic properties. We investigated subjects' use of ERs in their solutions to analytical reasoning problems. Two sources of data were analysed. The first consisted of a large corpus of ERs (`workscratchings') used by students in their solutions to problems administered via paper and pencil tests. The second source of data was collected using switchER, a computer-based system that administered the problems, provided a range of ER construction environments for the subject to choose between and which dynamically logged user--system interactions. SwitchER was developed in order to study the process and time-course of ER use and to investigate the mechanisms (such as ER switching) by which subjects resolve impasses in reasoning. The results showed great diversity of ER use across subjects, allowing the utility of various ERs under differing task conditions to be studied. The range of ERs used by subjects ...

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AbstractÐRecently, the first two in a series of planned comprehension experiments were performed to measure the effect of the control structure diagram �CSD) on program comprehensibility. Upper- and lower-division computer science and software engineering students were asked to respond to questions regarding the structure and execution of one source code module of a public domain graphics library. The time taken for each response and the correctness of each response was recorded. Statistical analysis of the data collected from these two experiments revealed that the CSD was highly significant in enhancing the subjects ' performance in this program comprehension task. The results of these initial experiments promise to shed light on fundamental questions regarding the effect of software visualizations on program comprehensibility. Index TermsÐSoftware visualization, control structure diagram, program comprehension, controlled experiments, evaluation. 1

Visual programming languages aim to broaden the use of diagrams within the software industry, to the extent that they are integrated into the programming language itself. As a result, they provide an ideal opportunity to study the benefits of diagrams as an external representation during problem solving: not only is programming a challenging problem-solving activity, but the effect of diagram usage can be directly assessed by comparing performance while using a visual programming language to performance with a standard textual language. There have been several misconceptions amongst visual language researchers regarding the role of diagrams in software design, but these are being addressed by empirical studies and by new theories of notation design derived from studies of visual programming. Based on this research, the authors are able to recommend several new directions for research into thinking with diagrams. Keywords: diagrams, diagrammatic reasoning, visual programming, ...

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...