Plot Automation
Reprinted from
The Journal of Computer Game Design
Volume 5, Number 1, (October 1991): pages 10-12
Copyright 1991 by David Graves
[email protected]
An automated playwright would allow interactive fiction plots to be developed
on the fly in the player's computer. At first look, it seems impossible to
develop software that could generate plot on the fly -- it seems the stuff of
science fiction. The holodeck on Star Trek, for example, is a computer-
controlled interactive fantasy that boasts of automated plot generation. One
might think that the hardware and software technology required to achieve
this goal are decades away.
However, after having worked on plot automation for several years, I am
convinced that the hardware and software technology required to develop an
automated playwright exists today. Why then, don't we all have them in our
games? One major limitation is our approach in writing interactive fiction.
I'm not saying that the existing form of IF is wrong, but I do feel that
there is room to extend the model for IF. After all, the IF genre has hardly
changed since it first appeared in the mid-1970s. Traditional interactive
fiction, for example, has been plagued by the "plot branch tree" concept --
few IF works have risen above this old paradigm.
In addition to changing the model we use for IF, I propose that we need to
extend our concept of story to make room for new modes of writing. I believe
that even if we (the development community) had a working software playwright
right now, we would be at a loss to develop story materials to feed into it.
This article addresses the paradigm shift required to develop and use an
automated playwright. Perhaps we can overcome some of the mental limitations
which keep us from realizing an automated playwright in our published works.
Why even bother developing an automated playwright? Interactive fiction
attempts to draw the reader/participant closer, by allowing him some choices
within the story. We have seen, though, how difficult it is for the IF
author to relinquish control to the reader/player and still end up with an
experience that tells a story. An automated playwright would bring new depth
to our IF creations by fulfilling the will of the author in a place where he
cannot be: within the home of reader as he experiences the story.
This brings us to virtual reality, a newborn technology with much potential.
I see some parallels with the beginnings of the computer game industry.
Today, you can stand in a virtual environment and play catch with another
person using a virtual ball. Doesn't that sound familiar? Will virtual
reality be a bigger, better environment for PONG? We need to be pushing on
plot automation right now, otherwise much of VR's potential will go untapped.
What about using an automated playwright in our current product, right now in
1991? Clearly, works of interactive fiction that utilized plot automation
would have a great increase in replayability. This would be tremendous
"value added" for each dollar the buyer puts down. Modern IF works may have
a rich interactive story, but they are typically a one-time experience.
One more reason to work towards plot automation: because it's the natural
next step in computer game evolution. Remember Aristotle's elements of
drama? Starting at the bottom of the hierarchy, you have spectacle
(everything that is seen), then music (everything that is heard), diction
(the selection and arrangement of words), thought (the processes leading to
choices and actions), character (patterns of choice; actionable attributes),
and plot (combinations of incidents making the whole action). Early computer
games allowed the player to manipulate objects in a physical world. The
focus was on the lowest elements of drama. Later we could simulate thought:
the computer opponent would make choices leading to action. In recent years
we have seen the emergence of character in games. Artificial Personality
supports the illusion that there is a character who shows recognizable
patterns to his choices; that he has attributes of his personality that are
revealed to us by his actions. This illusion is so intoxicating that we
willingly suspend all disbelief that the character and situation is
fictitious, and thus we are drawn in. The only step left in game evolution
is to allow the participant to have an influence in the plot, while an
automated playwright ensures that the combinations of incidents create a
whole, well-formed action. When you look at it this way, the creation of the
software playwright seems inevitable, doesn't it?
To re-iterate, the accepted model for interactive fiction is preventing us
from making progress towards plot automation. What, then, are the limiting
concepts that we seem to be locked into?
One: graphics depicting only physical world spectacle. This means that
graphics are used to show you what the fantasy world looks like.
Unfortunately, using graphics this way causes the plot to focus on the
physical world. It becomes too easy for the story developer to focus on
geography, because a fork in the road is the predominant example we see for
decision trees in real life. This typically leads to a "travel resistance"
plot.
Two: plot as a decision tree. In a plot tree for most games today, there
are failures at each of the "dead ends" of the tree. In early interactive
fiction, the protagonist would die at one of these nodes. In our more
enlightened times, the player does not necessarily die when he digresses from
the "true path", but the plot dies.
Three: viewing plot as a static construct. In traditional stories, the plot
is static. It has to be: the media is static. Words on a printed page
cannot change. Pick-a-path books allow us to make decisions, but the work
itself is still static, so the experience very soon becomes insipid and
uninteresting. Computer technology allows us to create works which are not
static, but our concept of "story as a static construct" leads us to create
interactive fiction in the form with which we are familiar. This leads to
over-scripting in our interactive stories. Then we are stuck with writing a
separate sub-story for each branch. Clearly, the IF author would have to
write much more story than the traditional author, if a work of IF is to have
significant variance in plot.
Let's look at each of these concepts in the traditional paradigm and ask how
we might make a shift in our thinking. First: graphics depicting thought
and character. This would allow works of IF that focus on characterization
and personality rather than focusing only on the physical world. Recall
Aristotle's dramatic elements, with thought and character on the higher
levels. While you cannot see "thought" in another person, their thoughts can
be partially revealed to you by their face. Their expression, nuance of eye,
lid, brow, jaw, and lip; each of these can provide a wealth of information,
some of which may be conflicting or ambiguous. Similarly, you can gain
insight into the "character" of a person by observing their expressions as
they react to a situation. This is critical to the artistic advancement of
our works. We cannot have a rich interpersonal fantasy experience in a world
which depicts only objects in a physical world, or a world which treats the
actors as objects to be manipulated.
Next: releasing more control of the plot. At the heart of interactive
fiction is interactivity. We present the player with choices, as a means to
draw him into the story. The player gets great pleasure from these making
choices. A skillful IF designer will give the player the illusion that he
has tremendous freedom. However, it seems that we give the illusion of
freedom to the player, then take it back again by using heavy scripting. In
order to ensure that the player experiences the full emotional impact of the
story, the author ensures that event A must precede event B. If we wish to
give some freedom to the player, and not take that freedom back again via
scripting, then we must release some of the control over the plot of the
story. Plot trees are the perfect model for organizing a heavily scripted
work of IF, so this suggests that if you wanted to create a work of IF that
was not heavily scripted, then a plot tree would not be the best structure
for organizing your story. I suggest that plot trees are useful as an
intermediate step in the development of a work of interactive fiction, just
as you would write an outline as a step in composing a paper. @From this
tree, you would then develop a plot network. Now the player may have a
number of plot experiences, rather than a single plot path. There will still
be some plot events that must precede others, but there will be more freedom
than before.
However, a plot network is still a static construct. You can draw a diagram
of it on a single piece of paper. It presents plot paths that the player may
traverse, but the structure of the paths is itself static. When we look at a
story this way, we are still seeing plot as data, and static data at that.
If we could view plot as a process, rather than as data, then we could begin
to rise above static plots. This is where the author begins to regain some
control. Assuming that the author has released control over the strict
sequence of events in a story, he can still influence the plot through the
rules he defines for a given story's plot process. The author crafts the
story by controlling it's content, not it's plot. She selects the scope of
the theme and the overall "message" of the work, which are exposed through
individual plot events. The process by which these "plot units" are
assembled is defined by the author's rules. The rules are applied at run-
time, in the player's computer, taking into account all that has taken place
in the story's progress so far, which includes the choices made by the
player. In effect, the player and the author write the work of IF together.
So, if we are able to view plot as a process, rather than as a static
construct, then we are freed from seeing plot as a sequence. Plot emerges
from a broad set of plot potentials. These potentials are loosely defined in
terms of plot units (which are static data), and plot rules (which can
interact dynamically). To exploit the potential of interactive fiction, it
is important to not nail things down. The nature of a specific plot is
unknown to the player, just as it is unknown to the author. The ambiguity
(in terms of the many variables and many rules) is what creates the
opportunity for different experiences in the same "story" definition. The
player gets to have a significant impact on the plot. The great increase in
replayability is the icing on the cake.
At this point it sounds like the automated playwright must be a huge program
taking up vast resources. How can we program that, let alone fit it into a
microcomputer? It turns out that the playwright does not need to make
decisions about each detail that happens in the story. In fact, the
playwright can sit back and watch the story go by tossing in a plot change
once in each five to ten minutes. You can get a tremendous amount of plot
springing forth from personality state. That's what Artificial Personality
is designed to do. It is pretty much accepted that Artificial Personality is
achievable today. Many story-games on the market show characters who can
make simple plans and display simulated emotions. Thus, the playwright can
focus entirely on high plot, since the Artificial Personality logic focuses
on Aristotle's thought and character. You can even allow conflict between
the playwright and the artificial personality logic, which will allow for the
generation of interesting plot conflicts. This represents the philosophical
argument of free will versus determinism. The playwright represents
determinism; it wants to see the plot go in a limited number of directions.
The Artificial Personality module represents the thought and character of
each of the agents in the story; thoughts and patterns of choice which might
be in conflict with each other, and in conflict with the playwright. This is
alright, though. Conflict is at the center of drama.
Okay, so if an artificial playwright existed now, how would people develop
material for it? Here is my proposed process: Write a story. Turn it into
a plot tree. (In traditional IF, you would be done with the design at this
step). Cut up the tree, such that pieces can be reassembled in a variety of
ways. You might develop a plot network as an intermediate step. Eventually,
though, you remove most of the static paths connecting plot units, replacing
them with rules that suggest how plot units might fit together. In a heavily
scripted story, the plot units would fit together only one way. Speaking
metaphorically, this is the equivalent of a jigsaw puzzle. In a loosely
scripted story, the plot units would fit together in a variety of ways. This
is the metaphorical equivalent of building blocks. Next, examine your set of
plot units and plot rules, looking for "dead ends", and fill these in with
additional plot pieces. It's important to do "path folding" so that a dead
end leads you back into the productive mainstream of the story's theme.
It is not technology that is keeping us from integrating the player's actions
into a computer assembled plot. We are limited by the mindset we apply to
this new area of opportunity. We cannot expect to move rapidly forward
carrying the baggage of the traditional interactive fiction genre. By
challenging our basic assumptions about the interactive fiction model, we can
exploit new technologies such as plot automation.
