The Trace Erasure Principle is a stipulation proposed by Noam Chomsky as part of the Generative-Transformational Grammar.
Under the Trace Erasure Principle, traces of a noun phrase (NP) can be replaced only by a designated morpheme and not by an arbitrary NP.
A case where this principle is not fulfilled can be the following: transformed into: Obviously, the meaning of the latter is radically different from that of the first.
We have replaced Mario with Maria, and their meaning is not linked.
But the following phrase fulfills the Principle: In this case, who identifies with Maria.