There's no legitimate scale for these sort of things, and the people who claim to have invented one are usually egocentric and insane and this applies to everything in my opinion; from that idiot sociologist who "developed" a legitimate scale of morality (of course everything that wasn't western, brainwashed, consumistic, capitalist was at the bottom) to that idiot of Piaget who "developed" a legitimate scale of cognitive growth (and of course school-based formal operations were at the top of the scale and emotional intuitive intelligence at the bottom) to that other idiot that "developed" the scale of acceptance and even that legitimate scale which is the IQ ... still thought by many as a "scale of intelligence" while there's no evidence that the IQ can test intelligence or knowledge or even intellect and while even the author of the IQ itself admitted it was not a tool to measure intellect skills (clearly so since it is based on sociocultural knowledge not on universal innate information)
So whatever scale some idiot has invented is just an idiocy (no matter how big the ego and aura of scientific rigour behind it) Art if possible is even more subjective, atemporal, anti-analytical, a-linear, global, intuitive, perceptive and instinctive and would refutes such kind of standardization. Of course someone could invent such scale and brainwash the world into believing it is the true rigorous way to determine objectively the interpretative degree ... but of course it would be nonsense and if someone had the gut to really see what the data actually says; it would see a reluctant reality never conforming to the standard and speculations of the scale.