Plotto is a book originally published in 1928 by William Wallace Cook that was recently (2011) republished by Tin House Books with an introduction by Paul Collins.
The point of the book is to provide
A classic how-to manual [...] Plotto is one writer's personal method, painstakingly diagrammed for the benefit of others [...] Cook takes his "Plottoist" through hundreds of situations and scenarios, guiding the reader's hand as a dizzying array of "purposes" and "obstacles" come to a head.
After familiarizing myself with its fascinating late-binding, finite automaton-like organization, I tried my hand this afternoon at creating the beginnings of a novel outline using Plotto.
If you've read this far, you might as well take a peek at it.