UMLR — Need example of derived qualifier.

Based on the results of UML25-322, it appears that the a qualifier can be a derived attribute. This is very powerful, as it allow for situational mappings to across the association. Please make this explicitly possible, best with an example.

I still believe a query function call would be the clearest. For example, I want to cross an association based on the name of a person

Hotel [map(guestName):enumeratedKey]--->* Reservation

This is very useful, needed by database modelers, and a very small, and limited change to the UML Spec.