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Here's another simple example. Imagine you had a single database file containing messages. Each message has a unique identifying 7 digit number. Each message also has a status, somewhat like an e-mail, of RECEIVED, READ, SENT and DELETED. Conceptually this might be arranged into an instance list like this:
| Business Object Type | AKey1 | AKey2 |
|---|---|---|
RECEIVE | RECEIVE | |
MESSAGE | RECEIVE | 26272 |
MESSAGE | RECEIVE | 63738 |
READ | READ | |
MESSAGE | READ | 73389 |
MESSAGE | READ | 74584 |
MESAAGE | READ | 73873 |
SENT | SENT | |
MESSAGE | SENT | 78383 |
MESSAGE | SENT | 37383 |
DELETED | DELETE | |
MESSAGE | DELETE | 62727 |
Conceptually the instance looks something like an e-mail inbox, outbox and deleted items. It is not directly reflective of the underpinning database design.