Equivalent of Aarne–Thompson–Uther Index for Science Fiction and Fantasy?

Several classification systems for fantasy (broadly defined, so as to include science fiction as well as ghost stories and elves, gnomes, and little men stuff) have been devised by science fiction fans, though I am not aware that any of them has been widely applied. For an overview of fantasy classification systems, see the Fancyclopedia entry for Classification of Fantasy:

Any attempt to tell outsiders "what fantasy (or science-fiction) is" brings the average fan up sharply against the fact that there are at least three major types of fantasy, as well as scattered stories which cannot be pigeonholed even under the subdivisions -- political fantasy, for instance.

Of the making of definitions there is no end, but bibliophiles really do need some standard for determining what is and is not fantasy. Intensionally, the essence of fantasy is probably imaginativeness; perhaps this accounts for its inclusion of some apparently unlikely subjects like stories of the prehistoric past or political fantasy. Considering fantasy extensionally brings us to the classification schemes worked out by several stfnists.

Speer defines the field of our interest by exclusion; using a three-dimensional time scheme, he categorizes mundane fiction as that which takes place in the present or the historical past, involving only the operation of known natural laws, and with the events lying within the bounds of what we know happened in the past of our history or is true of the present day. All fiction lying outside any of those boundaries is fantasy. Excluded from this class, however, are certain types that logically fall within it; religious imaginings (tho in early fantasyarns religious elements were sometimes present), fairy tales and children's animal stories (which do not come within the fantasy fan's field unless they are translated into another medium, like "Snow White" or The Jungle Book), and stories in which seemingly fantastic elements turn out to be hoaxes, like John Dickson Carr's "He Who Whispers" (tho the device of "it was all a dream", or that of a stranger telling a story the reader is not asked to believe, are so conventionalized that their occurrence does not remove the tale from the fantasy classification.) Tucker's suggested exclusion of salacious fiction with a fantastic background would be impossible without leaving obvious holes in the listing of contents of Amazing, Marvel, etc; but this sort of material is usually considered rather borderline. Also borderline are features which tho fantastic in nature do not influence the action of a story (for instance, a detective story in which an invention is stolen); these are defined as fantastic elements, and stories in which they appear are proper subjects for listing in bibliographies, etc.

Aside from the general question of classifying a given story as fantasy or non-fantasy, bibliophiles have worked to devise a classification system like that in use in libraries (Dewey Decimal and Library of Congress systems) or among scientific abstractors (Universal Decimal Classification). The three classical main divisions of fantasy -- science-fiction, pure fantasy, and weird fiction (each defined under its own heading in this volume), tho fundamental to a fan's orientation, are not suitable for main divisions of classification. For one thing, they often refer to the treatment a story gets rather than to the nature of the theme treated; for another, they are each so broad that there is much difference of opinion as to the exact coverage of each category.

Decimal systems of classification have been set up at various times by Sam Russell, Jack Speer, Langley Searles, and Alastair Cameron; of these, Speer's is by far the most widely used. (Cameron's has been praised as an excellent coverage of the field, but leads to so many multiple classifications that it has never been adopted.) To illustrate, categories of Speer's scheme are:

(1) The Future: Space travel; Extraterrestrial life and adventures on other planets; Extraordinary astronomical phenomena (e g destruction of Earth); Catastrophes to civilization (intensified Ice Age, plague, sole survivors, our barbarous descendants); Political, social, and economic life (oppression and revolt, matriarchy, decay of man).

(2) The Prehistoric Past: Prehuman life; early men; legendary civilizations; early historic cultures.

(3) Timespanning (including going forward and back in time, changing the past or the future, suspended animation, and might have been worlds).

(4) Impossible by contemporary science: Supernatural elements in the known world (wishes, charms, occult arts, curses, miracles, cults, haunted places and things, "possession", beings of religions, of medieval tradition and of modern conception); Unrationalized permutations and alterations (humanoid animals, unliving things personalized); Science's cosmology denied (as in subjective idealism); Life after death; Adventures in mythological worlds; Mythologies of modern conception.

(5) Extrapolations taking place in the present or the known past; Robots; Atomic energy; Invisibility; Super-speed; Duplication of persons; matter-radio television spyray and projector; laboratory creatures; strange animals and plants; non-carbon life; immortality; supermen; ESP; mind transference; Hypnotism (for old stories); lost Amerind and Arctic lands; Earth's Core; Subterranean life; subsea civilization; fourth dimension and two-dimensional; Macrocosm; microcosm [not in our sense, of course]; Littleness.

Substantially the same categories are used, in a different arrangement, by Russell's and Cameron's systems.

from Fancyclopedia 2 Supplement ca. 1960: Cameron's system, it's claimed, is a revision of Speer's -- though Cameron puts down Juffus's system in his preface --- and is actually less likely to lead to multiple classifications than the Speer method, according to Redd Boggs.

I believe the most famous fantasy classification systems are Jack Speer's {available here) and Alastair Cameron's, of which I have a paper copy somewhere around the house, but I don't know if it's available online.