Information Technology Reference
In-Depth Information
13.2.1 Preparing the Information
MEXICA employs two files to create its knowledge base: a dictionary of story-actions
and a file of Previous Stories. Both are text files provided by the user of the system.
The dictionary of story-actions specifies all possible actions that can be performed
by a character in a tale. The definition includes the name of the action, the number
of characters involved in it and the set of preconditions and post conditions of per-
forming such an action. As a distinctive characteristic, all preconditions and post
conditions in MEXICA are defined in terms of emotional links and tensions between
characters. Emotional links have an intensity and a valence; some examples are:
character A is very grateful towards Character B; Character A hates Character B;
Character A is in love with character B; Character A envies Character B. Examples
of tensions are: the life of Character B is at risk; the health of Character B is at risk;
character A is a prisoner; Character A is dead. Thus, the precondition to perform the
action A proposes B is the emotional link A is in love with B; the consequences of
the action A murders B is that character B is dead (a tension) and that all friends of
B that are aware of the murder hate A (an emotional link).
Notice how some of the preconditions and post conditions depend on cultural
aspects. For instance, if Character A rises his voice towards Character B, in some
cultures B might not care about it while in other cultures B might feel really upset. In
MEXICA, this situation can be represented by changing the intensity of a negative
emotional link. Thus, preconditions and post conditions are classified in two types:
logical and social. Logical conditions do not depend on cultural settings; for example,
the death of a character. Social conditions depend on cultural characteristics, for
example, an emotional response to a specific situation. In this way, the user of the
system has the flexibility to include some cultural aspects in his definition of story
actions.
The different events occurring in a story when it unfolds modify the circumstances
or context surrounding the story world. In this research, such circumstances are
called Story-Context. Thus, Story-Contexts are structures which represent the current
story-world state of affairs in terms of emotional links and tensions between charac-
ters. For instance, imagine a plot where Princess suffers an accident and then Jaguar
knight heals Princess. When the first action occurs the Story-Context registers that
the life of Princess is at risk (a tension); then, when the second action is performed,
the Story-Context is updated: the tension life at risk is deactivated and Princess is
very grateful towards Jaguar knight (an emotional link). Thus, the Story-Context is
a very dynamic structure that is refreshed each time an action is performed; it can
become a very complex construction comprising several emotional relations between
characters.
The Story-Context encodes the core events performed in the tale in terms of emo-
tional links and tensions between characters. In that way, it represents as a single
structure the consequences of a sequence of actions. As it will be explained later, this
characteristic is essential for the model.
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