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characters. For example, an author may have a goal to keep lovers apart; and, in
pursuit of this goal, he will insert into a story elements that prevent lovers from
meeting. It would be absurd for lovers themselves to seek obstacles to their
meeting; but as a device for enhancing a story's dramatic interest, it makes per-
fect sense for the author to devise such obstacles. Lebowitz's Universe program
generates plot outlines using an algorithm very similar to that used in Tale-Spin
except that author goals rather than character goals drive the mechanism. The
research issue addressed by Lebowitz treats the realization of an author's goals
in a story.
Scott Turner and Michael Dyer describe Minstrel (1985), a story-telling
program which generates believable and logically consistent stories that make a
point. Turner describes further development of Minstrel in subsequent papers
(Turner 1990, 1991a, b). Turner's primary interest is in modeling human cre-
ativity and human story-telling behavior, and he uses King Arthur-style tales as
his domain. Although we are working in a domain bearing superficial resem-
blances to Turner's, our objective is a model that is independent of the process
human authors undertake when writing a story.
A new grammar for stories
This section describes selected features from our formal model for simple
narratives (Lang 1997). The model takes the form of a definite clause gram-
mar, hereafter referred to as “the-grammar”. The nonterminals are meta-
components such as setting, episode, outcome, etc. The terminals are first-
order predicate calculus schemas for the events, states, goals, and beliefs which,
when instantiated and rendered into natural language, are the content of a sim-
ple narrative. The language described by the-grammar consists of lists of FOPC
expressions. Each list is an ordered representation of the facts and events con-
tained in some tale; but the list does not specify the relations among the vari-
ous terms in it. The example below shows an event list representing a portion
of “The Bad Wife.” The list adequately captures the states and events in the
story; but it does not represent the relationships among them. For example,
nothing in the list indicates that the trick carried out by the peasant at time
int(x7, x8) serves the goal held during time int(x10, x8) that his wife be in the
pit. The information about the relationships among the elements of the event
list is specified in the rules of the-grammar.
