Here is a protocol stimulated by Hanson’s ideas; it works both for ems and Keykos domains. A small number of entities (ems or domains) mutually enter a ‘meeting’ with the following agreement. They will be collectively confined yet able to interact. Each holds a capability to dissolve the meeting whereupon all participants return to their prior state upon entering and with only the mutual information of who cancelled the meeting. Upon unanimous agreement, the meeting concludes and the prior states are retired with meeting memories intact. This has some of the logic of optimistic concurrency protocols.
If the program of a domain X ‘wants’ to engage in a meeting, it is generally no big deal for X to create a new factory objects from which obey much the same code as the creator and thus have the same behavior. The requestor’s key is passed to the ‘meeting manager’.
When the meeting manager gets the requestor’s key for each of the participants, it gets a representative from each, endows it with the authority to communicate with the other meeting members, gives it the relevant meeting control authority and commences the meeting. The factory logic precludes outflowing signals but allows nearly arbitrary logic within the meeting, each participant safe from the others but in communication. Upon unanimous agreement the meeting manager returns the keys to each participant to the respective creator who thereby learns the outcome.
The participant’s behavior may be so close to the domain X who made the builder’s key that it could entirely replace X. We have not needed a ‘brain transplant’ in Keykos but it would not be difficult. After such a transplant (of state) all keys to the old domain would refer to an object with the state of the participant.