Currently, NamingSystem.replacedBy is a resource reference, referring to the REST endpoint where another namingsystem can be found. We fear this will not work well in situations where NamingSystems are put into registries - when registries each have a copy of the NamingSystem, the receiving registry would have to update this element to point to the NamingSystem within the same registry if it also has a copy of the replaced system.

Wouldn't it be better for this to be a fixed url, instead of a resource reference, that refers to one of the NamingSystem.uniqueIds?