In 2001, Zooko Wilcox-O'Hearn described the three desirable properties of network protocol identifiers to be global, unique, and memorable. The Zooko's triangle was named after Zooko Wilcox-O'Hearn, and its properties would later expand to become decentralized (global), secure (unique), and human-meaningful (memorable). Zooko's triangle represents the basic foundation of Petname models.
Human-meaningful identifiers need to pass what is known as the 'moving bus test' according to Wilcox-O'Hearn. The moving bus test is passed if the identifier can be remembered correctly for a definite period of time if seen on a bus passing by. An identifier is considered to be unique is it does not produce any collisions within the network and maintains a strong resistance against forgery.
Wilcox-O'Hearn claims that no identifier can satisfy all three requirements of desirable identifiers, and that only two identifier properties can be satisfied at once — this problem is represented by the visual analogy of Zooko's triangle. In Zooko's triangle, all three properties are connected with a single line, and only pairs at each corner can be connected using a single line. This visual analogy demonstrates that at one time an identifier can satisfy a maximum of two out of three desirable identifier characteristics of Zooko's triangle.
