Movements of interfaces can be analyzed in terms of whether they are expected, sensed, and desired. Expected movements are those that users naturally perform; sensed are those that can be measured by a computer; and desired movements are those that are required by a given application. We show how a systematic comparison of expected, sensed, and desired movements, especially with regard to how they do not precisely overlap, can reveal potential problems with an interface and also inspire new features. We describe how this approach has been applied to the design of three interfaces: pointing flashlights at walls and posters in order to play sounds; the Augurscope II, a mobile augmented reality interface for outdoors; and the Drift Table, an item of furniture that uses load sensing to control the display of aerial photographs. We propose that this approach can help to build a bridge between the analytic and inspirational approaches to design and can help designers meet the challenges raised by a diversification of sensing technologies and interface forms, increased mobility, and an emerging focus on technologies for everyday life.

We describe the design of tangible interfaces to the KidPad collaborative drawing tool. Our aims are to support the re-enactment of stories to audiences, and integration within real classroom environments. A six-month iterative design process, working with children and teachers in school, has produced the “magic carpet”, an interface that uses pressure mats and video-tracked and barcoded physical props to navigate a story in KidPad. Reflecting on this process, we propose four guidelines for the design of tangible interfaces for the classroom. (1) Use physical size and shysical props to encourage collaboration. (2) Be aware of how different interfaces emphasize different actions. (3) Be aware that superficial changes to the design can produce very different physical interactions. (4) Focus on open low-tech technologies rather than (over) polished products.

This paper proposes a technique based on information theory principles for shape description of 2-D images. By its essence the technique is invariant to rotation and translation. We first describe how the translational information content of an image may be defined, identified, assessed and analysed. The effect of the size is then assessed and quantified which permits us to propose a modified definition of translational information content invariant to scale. In order to demonstrate the feasibility of the developed techniques, a series of tests were carried out on rectangular and triangular shapes. The results illustrate the power of the translational information assessment techniques in analysing and describing 2-D images. The use of these techniques in shape description is also introduced.

This paper proposes a technique based on information theory principles for the assessment of the degree of dissimilarities between binary images. We first describe how the information content of an image may be defined, identified, assessed and analysed. This concept is then extended to the measurement of information content of more than one image. This information content measure is then shown to be related to the recognition information which is a measure of the degree of dissimilarities between images. In order to demonstrate the feasibility of the developed techniques, a series of tests were carried out on typed characters. The results illustrate the power of the information assessment techniques in analysing the recognition capabilities of a pattern recognition system.