1999 Conference Proceedings

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Dominique Burger
Marine Ferré Blanchard
Djamel Hadjadj
INSERM U483 - Université Pierre et Marie Curie


For years the telephone has been a media naturally accessible to the visually handicapped people who use it as a simple way to communicate with other people, to access information and to overcome some of the difficulties associated with their handicap. But the emergence of phone services requiring screen for more complex interaction with the end user, also called screen phones, not only creates a new barrier for visually handicapped accessing traditional services but also might exclude them from the new information society where telephony will be an important medium for accessing information and a great variety of services based or not on the Internet. [1][2]

The Vistel Consortium has been set up with the support of the EC to explore solutions to this problem and to demonstrate them [3]. In this paper we focus on the technical strategy followed in the project, presenting the general model of interaction and the adaptation technique that were used to adapt an existing screen phone.

The Vistel Problem

A General Model of Interactions

A review of a great variety of phone services made it possible to define a general model of interaction covering most of the interaction situations encountered. This model is based on five main principles:

  1. Standard functional components,
  2. Sequentialisation,
  3. Specific Guidance,
  4. Non verbal feed back, and
  5. Differentiated actions on Keys

Principle 1 : Standard functional components

A screen can be modelised using a five basic Interaction Components providing mechanisms to explore the content of the component and interact with it.:

Thus their meaning according to the context changes and their labels are refreshed on the screen. Soft Keys are problematic for visually handicapped users using speech adaptation, as they can not rely on a stable layout of the keys and would therefore easily perform wrong operations.

Nevertheless, all these components are quite traditional and non visual equivalents have been developed for the need of the visually handicapped users, in the context of MS-DOS or Windows, based on speech, Braille or magnified presentation of data.

Principle 2 : Sequentialisation

The presentation of data on a Braille display, or using a speech synthesiser, or magnifying the data on the screen, has to put the components in a sequence. The order of the components in the sequence will be chosen according to the context of the application and can be different for users who do not have the global view of the screen. Assuming that in the context of screen phone services the number of components in a sequence is limited, it is quite realistic to provide a very simple navigation mechanism based on two main function "Go a step forward" and " Go a step backward"'.

Principle 3 : Specific Guidance

Some extra guidance has to be provided to compensate the absence of a global view of the screen. This guidance can be given using textual comments just before an Interaction Component or just after.

Principle 4 : Non verbal feedback

Non verbal feedback is extremely useful in non visual interfaces in order to convey feedback rapidly. It can concern events that the user is expecting and wants confirmation about - like going to the next or previous line or element - or to give low level warning like "no more element after this one". Using beeps is a simple and low cost method to achieve this.

Principle 5 : Differenciated actions on Keys

Visually handicapped users may take advantage of the several possibility of pressing a key in order to get additional information before activating a command. This is particularly useful to solve the Soft Key problem. Pressing a Soft Key once gives information on the associated command while pressing it twice would activates the command.

It is worth noting here that this model is quite general and that it can be applied in quite different contexts. For instance it is fully compatible with the basic HTML elements and interaction components. Also this adaptation model implies simplification, reformulation, reorganisation of the data, as well as modification of the interaction principles used in the visual interface. This is what is called screen reconstruction.

Adaptation technique

The functions of the communication module are :