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of the tale. This set of actions, fluents, and characters is enumerated in a
world model.
Natural language output unit:
The story grammar and the world model de-
fine event lists: sequences of events which when rendered into natural lan-
guage constitute a story. These event lists are accompanied by the parse tree
describing the structure of the story. The event list and the parse tree are
rendered into natural language text to produce the final output.
Figure 2 illustrates the interaction among these components. The grammar
interpreter initiates the generation process by invoking the top level rule for a
story. When the generation process reaches a terminal, the grammar rule speci-
fies a
leaf schema
and requests that the world model instantiate it. A leaf schema
determines the form of the terminal and specifies how the world model el-
ements fit into the parse tree. When the grammar interpreter has produced
a completely instantiated parse tree and event list, these two structures are
mapped to surface text.
Wo r l d
Model
Natural
Language
Output Unit
Grammar
Interpreter
Story
Grammar
Temporal
Predicates
Request for
a story
Story in
natural language
Figure 2.
Schematic diagram of the relationship among the five Joseph components.
The world model
Coherence relations such as causality and goal-directedness are the “glue” con-
necting the story's states and events. By the
form
of a story, we mean these co-
herence relations among the constituent components. By a story's
content
we
mean the component states and events themselves. Our model separates rules
governing the form of a simple narrative from elements making up its content.
We implement this distinction by packaging the grammar terminals into a sep-
arate world model. The model Joseph uses to generate stories supports creation
of stories resembling Russian folk tales. The predicates in the model represent
