(Prequels are earlier in the z-space, but that’s hard to represent here.)
For an example and an explanation of how graph space works, read on.
Okay, the idea is simple: each point represents a spot on all three axes indicating how ‘same’ or ‘different’ it is. It’s easier to visualize if you can think about it in three dimensions and sort of guess as to which point each of my dots is supposed to signify.
In any case, this is a judgment call and you might completely disagree: thinking that the plot is more similar than I take it to be or claiming that I underestimated relevant differences in character development. Obviously, since the example is for a movie series with the character development of lemon pudding, I don’t expect these objections to arise.