== Registry Stability ==
it seems that the current policy does not make any assertions about
the stability of identifiers and their meaning. this means that it is
possible that identifiers get redefined by registry updates. many
registries avoid this kind of semantics shift by disallowing updated,
or only allowing updates that deprecate values. the reason is that
typically, registry contents will be used to write code and and then
any changes to entry semantics will break this code by redefining the
meaning of an existing value.
https://tools.ietf.org/html/draft-wilde-registries-01#section-3.5 makes the point that it is a common pattern to disallow updating
semantics. if that isn't done, i would recommend to add a note to
developers that identifier semantics may change, which probably will
break implementations, even though there is little they can actually
do about it.