3. Interface styles, modalities and interaction metaphors

From a formal point of view, all interaction is based on the use of language, i.e. rules (conventions) defining how sequences of symbols conveying the meaning of an exchange are organized. This language can take various forms. In humans, spoken language, written forms of language, including ideographic forms such as Chinese, and gestural forms such as sign language for the deaf are all examples of language forms.

In human-machine interaction, languages, which combine input and output expressions, can use different modes, including :

• text mode ;

• graphic mode. Graphic representations can be used to support direct designation;

• voice mode.

Although there is no strict relationship between the modes of expression used...