效绵鼎 Iterated Derivation =>*means“zero or more derivation steps.” Basis:a=>*a for any string a. Induction:if a=>*B and B=>y,then a=>*y. .12Iterated Derivation ◼ =>* means “zero or more derivation steps.” ◼ Basis:  =>*  for any string . ◼ Induction: if  =>*  and  => , then  =>* . 12