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The basic data structures in AI might be the rule, the frame, and the script ...but from a programmer's point-of-view these are really interchangeable - just arrangements of pointers in memory-space. So the real challenge is to discover which interpretations of these various arrangements of pointers best match the way human thinking works.
"Case-based reasoning" (CBR) tries to identify nodes with 'cases' - often actual realworld events that could (theoretically) be described to any infinite level of detail without being exhausted. A case is thus approximately equal to a story. But this sort of thinking, again, comes very hard to conventional computer hackers. If a story is infinitely complex, for example, how can it be indexed as more similar to some stories than others? (The solution to this paradox requires that we recognize some details within a story as more significant than others - an importance-ranking.)
In 1900, a French literary critic named Georges Polti published an analysis of literary plots entitled "The 36 Dramatic Situations" (reprinted 1977 by The Writer Inc, $8.95). Polti also further subdivided each of the 36 (citing particular plays and novels that embodied each variant), and included for each an enumeration of the basic 'elements' needed for the plot, e.g. for Supplication: "The dynamic elements necessary are: a Persecutor, a Suppliant and a Power in authority, whose decision is doubtful"
Here's a very rough re-sorting of Polti's thirtysix, according to a preliminary reworking of those elements:
person thing: Obtaining person motive: Victim of misfortune, Disaster, Ambition person motive motive: Self-sacrifice for an ideal person motive modality: Daring enterprise, Remorse person modality: Enigma, Madness, Fatal imprudence, Faulty judgment person person: Revolt, Familial hatred, Family rivalry, Conflict with a god, Loss of loved ones person person place: Recovery of a lost one person person place place: Pursuit, Abduction person person motive: Supplication, Victim of cruelty, Rivalry between superior and inferior, Crimes of love, Deliverance person person modality: Kinsman kills unrecognized kinsman, Obstacles to love, Mistaken jealousy person person motive motive: Revenge, All sacrifice for passion, Sacrifice of loved ones, An enemy loved, Self sacrifice for kindred person person motive modality: Involuntary crimes of love, Discovery of dishonor of a loved one person person person: Adultery, Murderous adultery person person person person motive motive: Vengeance by family upon family
Folklorists Vladimir Propp and Stith Thompson offered alternate approaches to the story-indexing problem, but Polti's remains the most useful for AI researchers, because (unlike Propp) it was constructed empirically ("bottom up") by surveying literature, and (unlike Thompson) it offers a manageable set of classes.
Abelson et al, at Yale, introduced the concept of scripts in "Scripts, Plans, Goals, and Understanding" in 1977. That book also recapped a primitive vocabulary called Conceptual Dependency (CD) notation, consisting of the following verbs: atrans, ptrans, propel, move, grasp, ingest, expel, mtrans, mbuild, speak, attend. While this proposal was far too simplistic to work, it has tenaciously dominated the field ever since (not to say sinisterly).
James Meehan's Yale thesis on his CD-based story-generation program "TaleSpin" was published as "The Metanovel" (Garland, 197?) and includes a hilarious chapter on the surreal stories that TaleSpin 'wrote' while being debugged. Later work in this Abelsonian school proposed a clumsy structure called a MOP (memory organization packet), then later (at NWU's ILS) a mulligan-stew called the Universal Indexing Frame.
The original programmer for the UIF (yours truly) was inspired, after wrestling at length with it on a low, data-structures-and-algorithms level, to envision a much more elegant structure he later named a "fractal thicket". (Unhappily, when he asked to present this idea to the lab, he was terminated!) The fractal-thicket data-structure is built on top of a simple abstraction hierarchy, each node of which can contain a (self-similar) image of the whole hierarchy (and on and on, as deep as one needs). This allows one to choose an arbitrary set of hierarchy-elements, and represent this entire set as one single particular node, as for example "person person place place" above. This could be neatly implemented with the 'eight-element cons cells' described above, so that sparsely populated regions never need to be instantiated in full. And such a structure will minimize the necessity for search, effectively substituting detailed indexing.
Another implication of this proposal is that anyone trying to represent knowledge can easily take their abstraction hierarchy, two elements at a time, and analyse these pairs for 'semantic content'. The first question to ask of such a set is, what are the basic relationships of these elements to each other? And these basic relationships should also form a natural story sequence. For example, the two-element combination "person thing" might imply the following chronology of relationships between a typical person and a typical thing:
person thing: wants, makes, acquires, uses, maintains, changes, disposes, destroys
There's a deep correspondence between these dyadic 'relationships' and what Minsky's frame-theory calls 'slots'. In fact, looking at it this way we should expect frames to suffer from a "Minsky bottleneck" - an inevitable tendency to bog down under thousands of slots, corresponding to every possible relationship the object can participate in. One logical solution is to sort the slots, by the types of their fillers... which is just another way of describing a fractal thicket!
The more-complex three-element set "person person thing" will certainly imply, among other stories, the obvious "gives" and "takes" and "contests".
And relationships themselves can be in relationship to each other:
relationship relationship: enables disables while causes followedBy etc
Here's a (tentative) further unpacking of one of the Polti-groupings above, for "person person motive":
Supplication: person asks person for motive Victim of cruelty: person causes (person suffers motive) Rivalry between superior and inferior: (person1 over person2) and (person1 gratifies motive) and (person2 suffers motive) Crimes of love: person indulges motive towards person
Person, place, and thing are obvious, familiar, basic categories. Motive and modality are somewhat less familiar:
thing: food tool weapon vehicle clothes bodypart etc (cf TADS) motive: food safety sex esteem family self-expression etc (cf Maslow) modality: real imaginary desired possible feared etc (cf Ortony)
The person-motive relationships:
person motive: suffers abstains denies gratifies indulges etc
...form a sort of mythic chronological sequence that I call the pride cycle. It forms the basis for James Joyce's universal inventory of story-elements, "Finnegans Wake" (1939). Joyce's earlier novel, "Ulysses" (1922) was a preliminary sorting of the universe of story-elements into 18 chapters, derived from episodes of Homer's Odyssey, which Joyce considered to be the most well-rounded portrait of an everyman, ever in literature. The 18 chapters cover a single day in the life of a humble Dubliner named Leopold Bloom. In order to pack every sort of story into Bloom's day, Joyce transforms them via metaphor into completely mundane everyday details. Analysis of Joyce's AI here has barely been begun by scholars, who have further tended to dismiss FW as a perfectly baffling mystery.
Joyce, an avowed Aristotelian who is known to have owned Polti's book, found it necessary in his work to challenge fearlessly all the taboos of the literary censors. Anyone who tries to inventory the whole range of the human experience must follow Joyce here, and this requires a level of self-honesty that has never been emphasized in AI research!
An article about Interactive Fiction design relative to the Wisdom-FAQ list is available.
Also a longer look at 'fractal-thicket indexing'.
Chris Crawford has a new approach to story generation via his Erasmatron story engine.
The ILS tech report about the UIF, and others, can be ordered for a few dollars from ILS.
Ftp to ftp://ftp.mcs.com/mcsnet.users/jorn/ and get