For a tree t rooted at N R with a height n, let T be the set of leaf nodes, and let F be the set of furcation nodes, and let ξ(N i , N j ) denote the length of the shortest path from N i to N j .
type-I Identification -Simple/Complex/ Compound/Complex-Compound: PCFG trees do not provide this information directly, hence we must construct an algorithm to derive it.