We compute the intersection of the edit script turning the parse tree into the generalize gold with the edit script turning the native gold tree into the generalized gold, and discard its cost.
if parse1 and parse2 are compared against gold1 and gold2 respectively, and if we set gold3 to be the result of gold1 t gold2, then δ new is defined as:  Now, if gold1 and gold3 are identical, then ES * (gold1,gold3)=∅ and we fall back on the simple tree edit distance score δ new (parse1,gold1,gold3)=δ(parse1, gold3).