We agree with the suggested addition of the $translate-id operation with these changes: Add optional parameters for 'preferredOnly' and 'date'.  If preferredOnly = true then return only the preferred identifier, or if preferredOnly = false then return all available ids.  If 'date' is supplied return only ids that have a validity period that includes that date.  The 'return' is a parameters resource including the identifiers and associated preferred flags and valid periods.  If multiple ids are returned then the client needs to determine what to do.  The 'return' may in some cases be drawn from multiple NamingSystem resource instances.