A Formal Framework for Design and Validation of Multimodal Interactive Systems in Transport Domain - Human-Computer Interactions in Transport - page 94

[COU 95] (user oriented), which enable the usability of the interface to be verified
via properties of flexibility 1 and robustness 2 .
4.2.1. Types of multimodality: CASE space
The CASE space [CAE 91] proposes classing the multimodality according to two
axes:
- the usage of media (parallel or sequential) , which specifies whether the media
are used sequentially (one after the other) or in parallel (at the same time);
- the links between information (combined or independent) , which specify
whether there is a semantic link between the information exchanged during the
interactive task (introduced in input or presented in output) by the different modalities.
The crossing of two values of each of these axes below gives birth to the following
four types of multimodal interaction:
- concurrent (parallel and independent) : the use of media is parallel and the
information expressed by the different modalities is semantically independent. For
example the redimensioning of a graphic object by the user sliding the mouse at the
same times as opening a new window by vocal command by microphone;
- alternated (sequential and combined) : the use of media is sequential and the
information expressed by the different modalities are semantically dependent. For
example, the result of the train times request, given to the user by the phrase “ the
train times are the following ” by vocal synthesis on a loudspeaker followed by the
timetable displayed on the screen;
- synergistic (parallel and combined) : the use of media is parallel and the
information expressed by the different modalities is semantically dependent. For
example, the vocal command “destroy this” on a microphone given when clicking
on the object of the interface;
- exclusive (sequential and independent) : the use of media is sequential and the
information expressed by the different modalities are semantically independent. For
example, giving the temperature on the screen followed by the announcement of the
humidity level on the loudspeaker.
The CASE space was refined, in [BEL 92, BEL 95], with the aim of distinguishing
the parallelism relative to the production of statements. It proposes to cross three
axes: production of statements (sequential/parallel), use of media (exclusive/parallel)
and the number of media by statement (one/several). This results in seven types
1 System ability to offer several possibilities to perform a task.
2 System ability to prevent errors and increase the user success probabilities.