Meehan's(1976) TALE-SPIN program is evaluated as a good starting point for the purpose of this paper. TALE-SPIN is a working program constructed in accordance with a more general framework for human cognitive behaviour developed by Schank and Abelson(1977). Meehan's work implies a theory of story writing (that stories are about purposeful behaviour of characters) which is later criticised and further refined. Since TALE-SPIN, a number of other projects have started which attempt to go beyond it. Dehn's(1981) AUTHOR, and Lebowitz's(1985) UNIVERSE are two such attempts, which address some of the shortcomings of TALE-SPIN.
The next scenario, although similar to the first, produces a larger set of stories as its output.
An example of such a system is the popular American story generation amusement called MAD-LIBS. These are collections of short (2-3 paragraph) story templates into which people are prompted to insert words by syntactic category type and delight in the surprising stories produced.
The main problem with variations of this scenario is that it tells us little about the creative nature of story writing. Nevertheless, it can be argued that a sophisticated version of it is actually used by some authors. For example (Schank, 1982) it has been claimed that some authors produce a new story by varying a known story. This point seems to be taken up by Schank(1982, 1984) in his study of human memory. He argues that when understanding a new story we are sometimes reminded of stories we have heard and stored in our memory before. This is because 'we must have been using a structure that was general enough to cover both stories.' These pairs of reminding events on the surface may be radically different, as the following example from Schank(1984) shows:
'X described how his wife would never cook his steak as rare as he liked it. When this was told to Y, it reminded him of a time, 30 years earlier, when he tried to get his hair cut in England and the barber wouldn't cut it as short as he wanted it.'
If people's memories are filled with detailed, flexible representations of past events and stories then there is no reason to doubt that they would use some of these as the bases for generating new ones.
A further argument for the use of approaches similar to the one described above (and procedural templates of Klein's approach described below) is that some writers have to produce text within a clearly defined genre and therefore have little choice but to follow a tradition. One of the tasks of the literary critic is to identify the restrictions which bound the text by the tradition of the genre and find rules governing the making of these restricted choices. Pemberton(1989) is an example of generation of stories in a restricted genre (the Medieval French Epic).
Figure 2.1. Sample output from Klein's(1973) program.
Polti(1916), Orwell(1948), Koestler(1969) and many other authors seem to indicate some sort of support for this approach where six (or sometimes seven) is mentioned as the number of universal plots, all stories being variations of these. Koestler(1969) presents the following:
The Promethean striving for omnipotence. Individual against society. Polygonal patterns of libidinous relations. War of sexes. Love triumphant or defeated. The conquest of the flesh.
Koestler(1969) considers these some sort of grouping in the catalogue of Goethe's 36 dramatic situations which are listed and classified by Polti(1916).
Propp(1968) also records 31 instances of what he calls 'functions of dramatic personae'. The importance of Propp's work, however, is not only in its classification of these elements, but in his attempts to find the structural relationship between these elements in the form of a grammar. It is this work which has led to the more elaborate attempts of Van Dijk(1972) and Kintsch and Van Dijk(1978) to argue for the existence of text grammars. However the general issue of 'structuralism' and whether there are concrete structures to social life which are reflected in structures in folk tales is out of the scope of this paper.
Propp's (1968) work has been developed by other Russian researchers of the 'Generative Poetics Movement' to a fine point for generation of literary text.
'The initiators of Generative Poetics assume that the artistic qualities of any given text can be accounted for through a finite small set of technical devices which they call Rules of Expressiveness. This set is fixed in advance, and it is the same for all texts of our culture. The immense variety of texts emerges as a result of an infinite variety of combinations (superpositions) of the Rules and of artistically amorphous everyday life material used by the artist.' (Dreizin et al, 1978)
Dreizin et al(1978) have proposed the use of Sceglov and Zolkovskij's(1975) Rules of Expressiveness for 'computerized generation of sacred legends'. This approach is by no means completely new to linguists. Dreizin et al intend to apply a finite set of (ten) rules to a 'theme' ('the message of the text') successively to transform it stage by stage until finally they get the story out.
A possible 'theme' would be:
INJURE (COMMUNITY(Arabs),COMMUNITY(Jews)) & Miraculously * (PROTECT(SACRED-POWER,Jew)) & Miraculously * (INJURE(SACRED-POWER,Arab))
The set of transformational rules ('Rules of Expressiveness') is as follows:
The scenario for this approach relies on the rules being ordered in such a way that a terminated transformation may be obtained by the successive application of the rules. Two of the simplest methods which can be applied are:
A. Breadth First Method
By contrast, Meehan(1976), attempts to 'model people making up stories'. The result is a 'theory' of story writing, and a program called TALE-SPIN based on it, which actually generates some stories. Meehan's theory of stories is a clear and simple one: that 'a story is about a problem and how it gets solved'. TALE-SPIN is a computer program which writes stories based on the above theory; 'by simulating a world, assigning goals to some characters and saying what happens when these goals interact with events in the simulated world'. The program, however, is not totally independent of the reader.
'The reader (the user) gets to supply much of the information about the initial state of the world, such as the choice of characters and the relationships between one character and another.'
Then the reader chooses the problem which the story is all about, out of a set of only four problems. From then onwards the story generation is a report of a problem-solver.
'At the heart of TALE-SPIN is a problem-solver, a program which implements a new theory of planning. Accordingly, the stories TALE-SPIN produces are essentially accounts of what happens during the course of solving one or more problems. This is consistent with the theory that all stories are about problems.'
GEORGE WAS VERY THIRSTY. GEORGE WANTED TO GET NEAR SOME WATER. GEORGE WALKED FROM HIS PATCH OF GROUND ACROSS THE MEADOW THROUGH THE VALLEY TO A RIVER. GEORGE FELL INTO THE WATER. GEORGE WANTED TO GET NEAR THE VALLEY. GEORGE COULDN'T GET NEAR THE VALLEY. GEORGE WANTED TO GET NEAR THE MEADOW. GEORGE COULDN'T GET NEAR THE MEADOW. WILMA WANTED TO GET NEAR GEORGE. WILMA GRABBED GEORGE WITH HER CLAW. WILMA TOOK GEORGE FROM THE RIVER THROUGH THE VALLEY TO THE MEADOW. GEORGE WAS DEVOTED TO WILMA. GEORGE OWED EVERYTHING TO WILMA. WILMA LET GO OF GEORGE. GEORGE FELL TO THE MEADOW. THE END.
Figure 2.3. Sample output from TALE-SPIN
These two modes differ in the level of detail at which the simulation is reported. The decision on the level is a static one independent of the story itself. These two levels could more appropriately be called a writer's assistant. Mode 3 of TALE-SPIN, however, employs a top-down strategy.
'How do you make it interesting?' asks Meehan(1976). 'You fix it in advance. You rig the world so that if people do behave rationally they'll do some interesting things... It models a writer who has something in mind that he wants to tell a story about... This is TALE-SPIN's mode 3.'
Mode 3 of TALE-SPIN is called the AESOP-FABLE GENERATOR. An example is the generation of 'The Fox and the Crow' with the moral 'Never trust...': 'We predict that A has some goal which requires that B be kindly disposed towards A, so A says something nice to B, B reacts accordingly, something happens which causes A to achieve his goal and also causes B to suffer.'
'The program which tells the story asks the reader for two characters (A and B) and attempts to tell the 'Never trust flatterers' story by finding some food or property in common... It asserts that A is being dishonest and that B is vain. Then it gives A the goal of being near B. The simulator then takes over.'
The AESOP-FABLE GENERATOR mode of TALE-SPIN, whilst retaining the general purpose simulation facilities, guarantees success by imposing a level of conformity to pre-existing story structures. This mode therefore can be seen as a compromise between the uncontrolled simulation of modes 1 and 2 of TALE-SPIN and the work of Klein(1973, 1975) and other 'reproduction' oriented scenarios. We shall not attempt to present a programmatic version of this scenario here as this point is discussed in detail in other parts of this dissertation.
'HENRY ANT WAS THIRSTY. HE WALKED OVER TO THE RIVER BANK WHERE HIS GOOD FRIEND BILL WAS SITTING. HENRY SLIPPED AND FELL IN THE RIVER. HE WAS UNABLE TO CALL FOR HELP. HE DROWNED.'
I find more interesting stories, such as the one below, among the MIS-SPUN TALES than among the boring correct ones.
'ONCE UPON A TIME THERE WAS A DISHONEST FOX AND A VAIN CROW. ONE DAY THE CROW WAS SITTING IN HIS TREE HOLDING THE PIECE OF CHEESE. HE BECAME HUNGRY AND SWALLOWED THE CHEESE. THE FOX WALKED OVER TO THE CROW. THE END.'
These stories above are interesting because they are different from Aesop's version of them. If a human writer were to rewrite Aesop's fables they would be different from the original as they would catch the flavour of the personality of the writer (for example fables by James Thurber, La Fontaine...). The capability to generate stories similar to the MIS-SPUN tales would be a worthwhile exercise in its own right. However these stories would be of use only if the framework within which they are produced could recognise their interestingness. Unfortunately Meehan's theory of story writing not only fails to appreciate this, but explicitly rules out these stories as 'wrong' stories.
It would be a challenge to produce a TALE-SPIN-like program which deals with more complicated situations (such as stories with two or more main characters) without having to change the theory that the stories are just about the problem solving of the characters.
One solution would be to monitor the problem solving of different characters, letting some achieve their goals and suppressing others. In order to be able to produce a coherent story, the monitor needs to have some other notion of what the story is about. The monitor starts becoming a complicated mechanism in order to manipulate the characters and their problems for the production of the story. At this stage the monitor needs to have goals of its own and plan the story.
De Beaugrande and Colby(1979) have formulated 'a basic set of plausible STORY-TELLING RULES' which introduce recursion, failure (in addition to success) of the goal and multi-character situations to the previous scenario.
What sort of characters should one create? What would be the reasons for choosing a certain character rather than another one? What sort of problems should one give the characters? From where does one obtain one's Micro-worlds?
Some of these questions have been subsequently addressed by Lebowitz(1984) and Dehn(1981) as well as by this author in papers published prior to this dissertation(Yazdani, 1982 and 1983).
Dehn(1981), in order to account for the author's intentionality, abandons the simulation approach of Meehan altogether. To the program AUTHOR (under development) 'the character is a modelling clay like the rest of the story world'. In this system 'a large part of the work of making up a story is the successive reformulation of the author's goals'.
While TALE-SPIN uses representations of the knowledge about the world and characters, AUTHOR uses representations from an author's memory. The system starts by attempting to reconstruct something from the memory in the reverse fashion to 'remembering'. A crude scenario for AUTHOR is a 'loop' constructed as follows:
TALE-SPIN's use of the physical world is very limited as it is created as a consequence of creating the characters. The characters themselves only have a simple schematic representation. The values of the slots in these schemes are filled by the reader, or by the 'plot' in the case of mode 3. Lebowitz(1984) addresses this shortcoming with a writer's aid for creation of story-telling universes comprised of characters, their histories, family relations and interpersonal relationships.
This work is motivated by the fact that a good deal of the work of television script writers is done by their keeping track of characters and their histories. These characters are created deliberately to satisfy specific constraints before any story telling takes place. Simulations of characters' behaviour take places in the UNIVERSE program in order to build up histories of characters' past lives. There is currently no algorithm for generating stories in the system.
The work of Lebowitz demonstrates the richness of creativity in the production of settings for stories. UNIVERSE builds on the structures used by Schank and Abelson(1977) in order to produce personal frame information for each character consisting of a name, stereotypes, trait modifications, goals, interpersonal relationships, marriages and lists of events in the characters' past history. The personality stereotype not only incorporates the numerical scales but also includes references to a set of built-in schemes for professions (doctor, lorry driver), social background (preppie, working class), race (Irish, Polish), religion (Catholic, Jew) etc.
Although UNIVERSE as yet does not produce stories, its overall aims are somewhat similar to the present dissertation as acknowledged by Lebowitz(1984) himself. The choice of characters is ultimately motivated by authors' goals such as those proposed by Dehn(1981) or Yazdani(1982, 1983). Therefore the method of creating characters should be at the service of other levels of the story generation system.
Dehn's AUTHOR is a conceptually neater solution for the problem of control, where known stories or memories of an author are the bases of generalisation for newer ones. Lebowitz's UNIVERSE points out the importance of building a rich world within which the stories could take place. These three programs, TALE-SPIN, AUTHOR and UNIVERSE therefore represent simulator, plot-maker and world-maker respectively of the process-based model which is reported in Yazdani(1982).
At first glance the scenarios presented here seem to be radically different in their approaches. Indeed the merits of one against the other is the subject of a continuing controversy. The two sides of the argument try to show that either 'real world knowledge' or 'transformational structure', is the basis of representation, understanding and generation of stories.
If 'real world knowledge' and 'transformational structure' were to be complementary things then most of the controversy disappears. All the scenarios above 'manipulate representations', be it on the surface or semantic levels. Our model manipulates multiple representations of 'the world', 'abstract communicative intentions', 'goal directed social behaviour', and 'narrative structures', as well as the grammatical structure of the language.
BEYOND TALE-SPIN
TALE-SPIN deals with the case where there is only one character solving one problem at a time. However, if more than one character had goals which they actively tried to achieve, then the simple problem solver of the TALE-SPIN would not be able to cope with the situation.
Figure 2.4. de Beaugrande and Colby's(1979) rules
However, de Beaugrande and Colby's more sophisticated version of Meehan's scenario is still open to many questions. DEHN'S AUTHOR
The major problem arises from the fact that Meehan, as well as Beaugrande and Colby make the intentions of the writer implicit in the program (e.g. in postponing goals) rather than explicitly stated and open to manipulation. What about a writer who intentionally wants to write a story as a form of communication, e.g. as propaganda or communicating a moral?
As most people who construct computer programs know, closed loops are dangerous components for a computer system. Dehn does not specify what terminating conditions her system would use and in what way the system would avoid becoming side-tracked into producing unrelated episodes. On the contrary, all 'essential characteristics' of Dehn's proposal - 'unforeseen opportunities', 'willingness to be distracted', 'successive reformulation', 'keeping the author usefully occupied', and 'providing new environments in which fortuitous opportunities are likely to arise' - seem to encourage a never ending stream of episodes. No recent reports of success or failure of this project have been published. LEBOWITZ'S UNIVERSE
A sound knowledge of both the physical and social world is needed by anybody who wants to write (or understand) stories. The world in which the story takes place is a rich source of creativity. The physical world not only contributes to the setting of the stories, but actually becomes an actor in some stories, such as those with the theme of human versus nature. CONCLUSIONS
The first three scenarios presented in this paper clearly point out the effectiveness of using pre-existing story structures in production of new ones. Meehan's TALE-SPIN on the other hand shows the power of simulation of purposeful action in a world. As the simulation on its own does not guarantee success in producing stories, the AESOP-FABLE GENERATOR attempts to control (or lead) the simulation in the direction of an existing story structure. Therefore represents a halfway house between using canned stories and undirected simulation.