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desired. The intermediary values enable the expression of intermediary levels
between these two extremes, so as to express levels of preference.
- At an attribute : we then specify a function defined over all the possible values
of this attribute and with values in the real interval [0, 1]. This function indicates the
weight given to each possible value of the attribute. The meaning of these weights is
the same as before. Thus, the values of attributes close to 1 are desired; whereas
values close to 0 are not, and a weight of 0 might even be refused.
A profile (such as previously mentioned) is defined as being a weighting tree,
the root of which corresponds to the root of the taxonomy of modalities. Figure 10.7
gives an example of a partial profile. It could correspond to a blind English-
speaking user, who would much rather have auditory modalities to visual ones: the
corresponding weights are shown in white on a black background, next to the nodes.
Weighting functions are shown for a few attributes: depending on whether attributes
are with continuous variations or with discrete values, the weighting functions are
themselves continuous or discrete.
Figure 10.7. Example of partial profile (weighting tree)
Given a user u , a presentation device d and a semantic unit s, the definition of
the most adequate modality (and its instantiation) to present s to d over u, is realized
by carrying out the intersection of the three respective weighting trees. This
intersection mechanism [JAC 06b] ultimately produces a new weighting tree, the
leaves of which indicate the candidate modalities. All that needs to be done then is
 
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