┌──────────────── ⇦ ───────────────┐
    │             ┌ ⇦ ┐                │
    │ ┌── → ─── shareable ─── → ─── Monitor
┌ object            ⇧
└ ⇦ ┘ └── → ── transactable
                  └ ⇦ ┘
I've got → representing is-a relationships and ⇨ representing can-contain relationships.