+--------------+              +-------------+
| OWNER        |              | NODE        |
+---+----------+ <---+  +---> +---+---------+
|PK | OWNER_id |     |  |     |PK | NODE_id |
|   | other    |     |  |     |   | other   |
+---+----------+     |  |     +---+---------+
                     |  |
               +--------------+
               | MAILING_LIST |
               +---+----------+
               |FK | OWNER_id |
               |FK | NODE_id  |
               +---+----------+