Enhancing Believability of Virtual Soccer Players: Application of a BDI-Model with Emotions and Trust - Developing Concepts in Applied Intelligence - page 123

some instances of the sort STATE were { win_game , ball_in_possession , ball_nearby_goal ,
score_other_goal }, some instances of the sort BELIEF were { is_at_location(AGENT, REAL) ,
has_capability(AGENT, ACTION, REAL) , satisfies(ACTION, STATE) , opportunity_for(ACTION) },
and some instances of the sort ACTION were { shoot_at_goal , pass_from_to(AGENT,
AGENT) , dribble , run_free }.
To illustrate the behavior of the model, Figures 2 and 3 show some fragments of an
example LEADSTO simulation trace, addressing a simple scenario in which a number
of subsequent (positive and negative) events occur. In both figures, time is on the
horizontal axis. Figure 2 shows a number of actions that are performed during the
scenario by player Z, a teammate of player X. A dark box on top of a line indicates
that an action is being performed at that time point. Figure 3 shows the emotional
state (in this case the amount of happiness, on a [0,1] scale) that player X has with
respect to player Z.
Fig. 2. Example simulation results - Actions performed by player Z.
Fig. 3. Example simulation results - Emotional state of player X with respect to player Z.
As can be seen from the figures, player X's emotional state regarding player Z
changes as a consequence of player Z's actions. Note that it takes about 3 time points
in the simulations to change an emotional state, which explains the short delays. For
instance, at time point 7-9, player Z shoots at the goal. Apparently, this attempt is
appreciated by player X (i.e., it contributes to fulfillment of this agent's desires), since
at time point 10-12, the agent's happiness regarding agent Z increases from 0.5 to
0.55. Similarly, player Z's attempts to pass the ball forward (time point 19-25) also
lead to an increase of agent X's happiness. Note that not all of player Z's actions lead
to an increase of happiness. There are two potential causes for this: either the action
fails (not shown in the figure), or the action does not contribute to player X's desires.