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## Interpreting a Sequence Diagram

- Each key press results in separate call to `dial`, but only one is shown
- Connection wants to get greeting to play
- Each mailbox knows its greeting
- Connection must find mailbox object:
  Call `findMailbox` on `MailSystem` object
- Parameters are not displayed (e.g. mailbox number)
- Return values are not displayed (e.g. found mailbox)
- Note that connection holds on to that mailbox over multiple calls

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