"Containers participating in non local namespaces that also support legacy addresses MUST recognize the follow-
ing forms as equivalent where <domain> represents the name of the container in the non local namespace."

What does this mean? In general what relationships are we defining between containers and domains ?

In particular are we saying that for every container must support at least one "local" domain where for every address /domain/path you can also address it as simply path. Or are we saying that if a container supports addresses of the form "path" then there must be a single domain D such that /D/path is equivalent to path for all paths?