PART | III Multimodal Human-Computer and Human-to-Human Interaction
an information need, the user must express it with respect to relevant
(positive) and non-relevant (negative) examples . From there,
some form of learning is performed, to retrieve the documents that
are the most similar to the combination of relevant examples and
dissimilar to the combination of non-relevant examples (see Section
14.4.1). The question then arises of how to ﬁnd the initial exam-
ples themselves. Researchers have therefore investigated new tools
and protocols for the discovery of relevant bootstrapping examples.
These tools often take the form of browsing interfaces whose aim
is to help the user exploring the information space to locate the
The initial query step of most QBE-based systems consists in
showing images in random sequential order over a 2D grid .
This follows the idea that a random sampling will be representative
of the collection content and allow for choosing relevant examples.
However, the chance for gathering sufﬁcient relevant examples is low
and much effort must be spent in guiding the system towards the rel-
evant region of information space where the sought items may lie.
Similarity-based visualisation [47–55] organises images with respect
to their perceived similarities. Similarity is mapped onto the notion
of distance so that a dimension reduction technique may generate a
2D or 3D space representation where images may be organised. It is
further known that high dimensionality has an impact on the mean-
ingfulness of the distances deﬁned . This is known as the curse of
dimensionality (see Chapter 2) and several results can be proven that
there is a need for avoiding high-dimensional spaces, where possible.
A number of methods exist to achieve dimension reduction. We do
not detail the list and principles here but refer the reader to [57–60]
for thorough reviews on the topic.
Figure 14.1a illustrates the organisation of an image collection
based on colour information using the HDME dimension reduction
. This type of display may be used to capture feedback by letting
the user reorganise or validate the displayed images. Figure 14.1b
shows a screenshot of the interface of the El Niño system  with
such a conﬁguration.
Speciﬁc devices may then be used to perform search operations.
Figure 14.2 shows operators sitting around an interactive table for