Image Processing Reference
- agents always have an objective at their disposal. It is set by the knowledge
base. Starting with its initial objective, the system navigates through the goal space by
means of the focusing rules;
- depending on the concept to search for, agents have one or several methods at
their disposal in the knowledge base. For example, when searching for areas that rep-
resent the road concept, agents can rely on geometric information (Hough transform,
AREA) and radiometric information (gray levels).
Thus, the knowledge base allows connections between different representation
- a connection between the goal and the “how”: the knowledge base associates
each concept with localization, detection and focusing methods, which will then be
- a connection between the goal and the “where”: the knowledge base specifies
focusing strategies which enable to define new areas of interest for a new objective.
This variation in the three representation spaces gives the system great qualities in
adapting, distributing, incrementing as we will now discuss.
10.2.2. Focusing and adapting
According to the philosophy generally advocated by active perception and among
others by Bajcsy [BAJ 88], we have chosen a strategy that operates by consecutive
focusing steps, in other words a control guided by the search for information
[TOU 98]. Thus, when an agent extracts relevant information, it can request the
creation of another agent to obtain complementary information in a precise area of
the image. As a result, the system works out a strategy based on what it finds at a
given instant, and in that sense can be described as opportunistic. Depending on the
goal and the context, a method is selected in the knowledge base and its parameters
are adjusted locally by the agent.
Focusing and adaptation mechanisms are closely related. They make it possible
to improve the performances of a vision system by way of an active behavior of the
system. It is only possible to adapt the parameters and strategies of a system if a
focusing phase has been conducted beforehand.
These two concepts are also embedded in the three-dimensional “where, what,
how” space. As regards focusing, we will use the terms:
- spatial focusing: control in the image space;
- cognitive focusing: control in the goal space;
- operational focusing: control in the task space.