A Formal Framework for Design and Validation of Multimodal Interactive Systems in Transport Domain - Human-Computer Interactions in Transport - page 95

of multimodality (the configuration sequential production of statements and
simultaneous use of the media being impossible): exclusive, alternated, synergistic,
parallel, exclusive, simultaneous parallel, alternated parallel and synergistic parallel.
4.2.2. The CARE properties
HIC3 can be characterized by four properties [COU 95] that describe the relations
existing between the different modalities for the accomplishment of a task. These
properties enable us to appreciate the flexibility and robustness of a multimodal HCI:
- Complementarity : several modalities intervene in the interactive task and each
modality used is necessary for the interactive task. Example: the command “ put that
there ”, which combines speaking the phrase and clicking the mouse to select the object
and the site. Speech and direct handling are therefore complementary.
- Assignation (specialization) : the same modality (or subset of modalities) is
chosen for a given interactive action. Example: the change from one window to the
next is always done by the click of the mouse.
- Redundancy : several modalities intervene in the interactive task and the
modalities express the same semantics. Example: the presentation of the information
that “ there is no train that meets your request ” is done by vocal synthesis and by
displayed text. Thus, these two modalities are redundant for this task.
- Equivalence : the interactive task can be carried out by using different modalities
enabling the same result to be obtained with a cognitive cost that may be different.
Example: the presentation of information: “ there is no train that meets your request ”
is done by vocal synthesis or by text displayed; these two modalities are equivalent for
this task.
Thus, equivalence and redundancy that offer the user interaction variations favor the
flexibility and robustness of the interface. On the contrary, the assignation that means
the user has to use a particular modality for an interactive task contributes to the
rigidity of the interface and goes against the principles of flexibility and robustness.
Similarly, several modalities intervene in complementarity that are assigned to
different aspects and are complementary to the execution of an interactive task;
consequently, it is like assignation, source of a certain rigidity of the interface.
4.3. Formal design
Formal design consists of developing a system (software or material) by strictly
respecting a set of specifications. It is based on formal models and mechanisms of
validation either prior (proof of theorems, model checking )or after the fact (test).