NOT.5:2 - Problem

How can a change of notation make the next operation possible while keeping its answer connected to the source and exposing distinctions that can no longer be recovered?

Two source expressions can produce the same target expression. The target may still answer a useful question, but a reverse converter cannot infer which source was used from that target alone. A familiar default can conceal this loss. Conversely, requiring complete reversibility can exclude a cheap summary that is sufficient for the actual question.

A target edit adds another difficulty. There may be several source changes consistent with it, each preserving different features of the earlier source. Successful conversion in one direction does not choose among them.