The idea of compartments is similar to apartments
except that the tenant of a compartment is the machine owner or an invited guest.
(The compartment is much like an apartment that includes a delegate of a person.
The delegate presumably communicates with that person thru some secure channel.)
The owner may have computer business in a few compartmented parts of his or her life.
She may belong to a museum board and also be a CFO of a company, each with separate secrecy requirements.
She may need to allow friendly programs to operate in her computer but limited to the proper compartment.
Missives from other board members are routed to the mail queue in the museum compartment while e-mail on company business is automatically routed to a mail clerk in her company compartment.
Each of these compartments has its own name space that is made available to external programs that are allowed into the particular compartment.
Both compartments may, for instance, have an object (file?) called "roster".
The Museum roster will not be confused with the company roster because they are in different compartments.
I assume that the correspondents having access to the museum compartment have similar arrangements and that e-mail broadcast to the board by a board member may take beneficial action on the respective rosters of the respective board members.
I am not sure that this is a good pattern but it seems to me to be clearly better than the Microsoft model which would confuse the rosters of the museum and company.
The Microsoft model allows any e-mail with an active attachment to operate on any file in the whole computer whereas this scheme presents access to only those elements of the compartment. No external mail has access to system components for they are accessible in no compartment.
In the proposed model only objects (files?) in some compartment are accessible by external programs and then only from friends that are properly introduced to that compartment.
If the machine owner has different public keys for different compartments
then only e-mail encrypted with the compartmentalized public key can gain
access to that compartment and its elements.
The compartment and apartment mechanisms have much in common.
They have a name space where names have some conventional meanings beyond the particular machine.