Research alert

X.3 May + June 2003
Page: 9
Digital Citation

Designing human-computer interfaces for quadriplegic people

Constantine Steriadis, Philip Constantinou

Our method is based on the use of a specially issued software class called "wifsid" (widget for single-switch input devices), which can be regarded as a universal scan element. A wifsid is graphically represented by a combination of a bitmap image, a label, and a 3-D frame. The scanning process does not address how to turn a highlight on or off; each wifsid has its own mode of highlighting. Users’ inputs are captured through a 2-D array of wifsids; the arrays are then scanned and forwarded to the selected wifsid for further handling. The wifsid-array and the applied scan modes are encoded by special data structures, resulting in flexible and efficient, graphically improved, scanning-based interfaces. Also in the paper we compare a newly developed scan mode (diagonal selection mode) with three common scan modes (cell, row, and submatrix selection modes) and include some basic principles that the designers of such interfaces should keep in mind.

This methodology was applied to the development of our assistive software application called Autonomia. Autonomia was designed for Microsoft Windows environments and can be operated by a person who uses one switch. In accordance with the multiple windows that appear in ordinary graphical user interface (GUI) applications, multiple "frames" have been incorporated into Autonomia to enable a user to perform several tasks. Figures 1 a & b show snapshots of the frames that handle the two most common tasks for scanning systems: mouse and keyboard emulation. These snapshots show that our methodology can provide user-friendly interfaces in harmony with the spirit of modern GUI interfaces that most people use today.

A home user has been using Autonomia for almost two years, with encouraging results about its efficiency. Our patient is a 35-year-old male who has been suffering from amyotrophic lateral sclerosis (ALS) since 1997. He is currently bedridden and lost the ability to speak four years ago. We have acquired valuable feedback that helped us improve the application and design more useful and efficient frames. Using Autonomia’s keyboard emulation frame as a testbed, we also conducted a series of tests in order to evaluate the importance of several parameters of the scan process and how they affect a frame’s overall performance. Our tests proved that optimization of the matrices’ layout and use of a proper scan-mode greatly help speed up the frame’s performance. The diagonal selection mode seemed to perform well in the tests, although the subjects of our tests experienced some difficulties in becoming familiar with the mode.


Constantine E. Steriadis and Philip Constantinou
School of Electrical and Computer Engineering
National Technical University of Athens
Athens, Greece (Hellas)


This abstract is from a recent issue or forthcoming issue of ACM’s Transactions of Computer Human Interaction (ToCHI). It is included here to alert interactions readers to what research is being done in the field of Computer Human Interaction. The complete papers, when published, can be found in ACM’s Digital Library at


F1AF1BFigure 1. Snapshots of Autonomia’s mouse and keyboard emulation frames.
(a) Snapshot of the mouse-emulation frame. The wifsid that causes the cursor to move downwards is highlighted.
(b) Snapshot of the keyboard-emulation frame with word-prediction activated. The wifsids are located on a 9x9 matrix and the 7th row is highlighted.

©2003 ACM  1072-5220/03/0500  $5.00

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