Broken references are transitively immutable and are transitively passed by copy. Vertical Taxonomy A reference is either a Promise or Resolved . Messages sent to an Promise are queued, awaiting the Promise's resolution. Should the Promise become fulfilled, whether to a Near or Far reference, these messages will be delivered to that object. The result of an eventual-send always starts as a Promise for the outcome.
Promises are Unsettled.
It is locally known whether a Resolved reference designates an object or not, and if so, which object it designates. When the result of an eventual send becomes Resolved, we know that the request has completed, and that the reference now designates its outcome. Promises can become Resolved, but once Resolved always Resolved. If the result of an eventual send becomes Fulfilled, we know the request succeeded. In the latter two cases, the reference the message was sent on has failed, and will become Broken as well.