A-T-U classification system
Aarne - Thompson - Uther
The Finnish scholar Antti Aarne developed the first tale-type index in 1910, which was limited to European tales.
Stith Thompson expanded the work by translating and expanding Aarne's tale-type index. His work mostly covered European tales, with some Near Eastern tales categorized into different general, abstracted types. His work and Arne's work are called the "AT number system" collectively. The system assigned a number identifier and a title to each tale type, such as 510A Cinderella tale-type.
German folklorist Hans Uther later expanded the AT number system in 2004 with the publication of 'The Types of International Folktales: A Classification and Bibliography'. He finally developed the ATU system, or the Aarne-Thompson-Uther classification system and included tales from eastern and southern Europe as well.
7 Major Categories
1-299: Animal Tales
300-749: Tales of Magic
750-849: Religious Tales
1200-1999: Anecdotes and Jokes
1000-1199: Tales of the Stupid Ogre (Giant, Devil)
850-999: Realistic Tales
2000-2399: Formula Tales
how the system works
All tale types in the index are indicated "AT" or "ATU" to determine whether they are an original tale-type in Arne and Thompson's 1928 or 1961 index or whether they are revised by Uther in the 2004 index.
Each ATU index entry contains tale-type title, summary of plot, motif references, other tale-types with which it is often combined, comments, and bibliography of relevant scholarship.
ex. Cinderella
categorized under "Tales of Magic" in the ATU index
tale type 510 (ATU 510) or "The Persecuted Heroine"
ATU 510A "Cinderella" tale type and ATU 510B "Catskin" tale-type