Comment by delusional

> But in general, identifiers have little currency outside the system that generated them

That's clearly wrong, because if it were true we wouldn't be able to identify anything. Identifiers are only useful in so far as some external party assigns a meaning to the identifier. Two systems MUST pick a common idwntifier to discuss a person. They MUST pick an identifier to discuss a technical field. They MUST even pick an identifier to discuss a technical protocol.

Identifiers are everywhere. They'll usually be translated into something internal at the edge of a system, but I bet the PNR is too.