In this case, in order to manage the consensus with non-functional grammars, we decompose such a tree into two sets: a set of anchored categories X s and a set of anchored function labels F s .
a tree T can be described by means of two boolean vectors: • z(T ) indexed by anchored categories X s , z(T ) Xs = 1 if there exists a function label F so that (X, F ) s is in T , and 0 otherwise; • ζ(T ) indexed by anchored function labels F s , ζ(T ) Fs = 1 if there exists a category X so that (X, F ) s is in T , and 0 otherwise.