From MEXICA to MEXICA-Impro: The Evolution of a Computer Model for Plot Generation - Computational Creativity Research: Towards Creative Machines - page 269

comparing it against some references; in others, it involves establishing how much
some attributes are present within the plot. The system rates each of these aspects;
possible values range between zero and one. With all these information the program
calculates a final result. Details of the whole evaluation model can be found in Pérez
y Pérez [ 13 ]. The following lines describe the seven characteristics employed by the
current version of the Evaluator.
1. Opening: A story has a correct opening when at the beginning there are no active
dramatic tensions in the tale and then the tension starts to grow (see Fig. 13.2 a).
2. Closure: A story “should display an overall integrity and closure, for example with
a problem posed in an early part of the text being resolved by the conclusion”
([ 5 ]). Thus, the closure of a plot is adequate when all the dramatic tensions in the
story are sorted out when the last action is performed (see Fig. 13.2 d).
3. Climax: In the Tensional Representation the climax is characterised as the highest
peak in the figure. In order to evaluate it, the system gets the average value of all
Previous Stories' climax and employs it as a reference (see Fig. 13.2 c).
4. Reintroducing Complications: In this work, we support narratives that appear
to end and then new problems for the characters arise (i.e. where all tensions
are solved and then they rise again). We refer to this situation as reintroducing-
complications. MEXICA calculates the average number of complications that are
reintroduced in the Previous Stories and employs it as a reference (see Fig. 13.2 b).
5. Novel Contextual-Structures: A new story generates new knowledge when it
generates structures that did not exist previously in the knowledge base of the
system and that can be employed to build novel narratives.
6. Original Value: Besides calculating the number of novel Contextual-Structures,
it is necessary to determine how original they are with respect to the information
that already exists in the knowledge base.
7. Preconditions: All actions' preconditions, which represent common sense knowl-
edge, must be satisfied. MEXICA verifies if this requirement is fulfilled.
After evaluating the plot MEXICA generates a report which includes the final
result as well as some comments explaining the reasons that lead the agent to give
that particular mark. The following lines show the evaluation of MEXICA's story
introduced in Sect. 13.2.4 .
EVALUATION OF THE STORY
This story is really good! I like it! Congratulations!
Here are some comments about your work that I hope will be a useful feedback.
COHERENCE
The story is very logical; all actions are nicely integrated and form a coherent unit.
It has a clear closure where all conflicts are worked out. Nice!
INTERESTINGNESS
The text has a good introduction.
The story reaches a nice climax with a good amount of tension. This is an important char-
acteristic of a good narrative. Great!
The enjoyable closure of the story makes the reader to connect nicely with the plot.