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Fig. 2. Perception-Decision-Action loop
perception 2 (new events, leak, fire, an order, a changing state), the agent sets
up its characteristics, its goal, its control mode and then the decisional process
decides the next action (task) to perform. This decision generate an action in
the environment which can succeed or not. Fig. 2 illustrates this mechanism.
4
Decisional Process
4.1
Task Representation
To represent agents activity we use HAWAI-DL 3 language that consists of a
formal description of the task as an arborescent decomposition beginning from
the more abstract task (root) decompose with subtasks until the lower level, the
action (leaf). The description of the activity integrates individual features and
situational constraints. A task is constitute with three parts : the core, relations
with the world and the link with the objects.
The core corresponds to all the information needed to describe the task. Re-
lations with the world are the world states managing the execution of the task
(starting conditions, realization or stop conditions).
The scheduling of the subtasks of a task is defined by different types of con-
structors: SEQ (subtasks are executed in the given order), ALT (only one subtask
is executed), AND (subtasks are executed in any order and do not share data
and resources), OR (subtasks are executed in any order and at least one sub-
task is executed), PAR (subtasks are executed in any order and share data and
resources), SIM (subtasks are executed at the same time).
The context of realization of the task is described with preconditions at-
tributes. The consequences of the task execution is describes with post-conditions
attributes. For the preconditions we distinguish :
2 Perception is the ability to take in information via the senses, and process it in some
way.
3 Human Activity and Work Analysis for sImulation-Description Language.
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