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and instantiation of modalities is done in a decentralized manner. Given the
disseminated nature of entities involved in an ambient intelligence system, it is
advisable to adopt a decentralized approach, in line with the architecture induced by
the previously described agents. Thus, when an entity U penetrates the space of
influence of an entity P, the two agents associated with these entities will negotiate
to determine the most adequate modality (and its instantiation) to use in order to
present information to U. This negotiation process is based on the notion of
profiles
.
A profile is a set of weights assigned to modalities and their instances. Profiles are
defined in relation to an arborescent taxonomy of modalities, common to the three
types of entities. Figure 10.6 gives an example of a partial taxonomic tree of output
modalities.
Figure 10.6.
Example of a partial taxonomy of output modalities
Each entity defines a weighting tree that it will superimpose over the taxonomic
tree of modalities
4
. The principle of a weighting tree is simple: it consists of adding
weights to a taxonomic tree in order to express the abilities, preferences and
constraints of users, devices and semantic units. A weight is a real number between
0 (included) and 1 (also included). It can be situated in two different places:
-
At a node
: the weight then applies to the sub-tree that has this node as its root.
A weight of 1 means that the modalities of sub-trees are accepted, or even desired;
whereas a weight of 0 means that the corresponding modalities are refused or not
4 Except for K entities, which define a weighting tree for each semantic unit that they
produce. Indeed, each semantic unit is likely to be able to express itself according to its own
modalities. Consequently, in the case of K entities, the weighting trees are attached to
semantic units produced and not to the entity that generates them.