The example on the page don't really do it justice, because both of them are O(4), and the time delay is arbitrary.
The "" example should only consist of 3 operations: Dawn: REQUEST, Tim: RESPOND, Dawn: CLOSE. For example: "Hiya! What time was that thing?", "hey, 3:30", "Ta - seeya then!". Or even just 2, Dawn: REQUEST, Tim: RESPOND (auto close), this could imply that Dawn and Tim are really close, or really not close.
BTW: We are not designing reliable messaging protocols here folks. The chat software should tell if any message was lost.
The "" example should only consist of 3 operations: Dawn: REQUEST, Tim: RESPOND, Dawn: CLOSE. For example: "Hiya! What time was that thing?", "hey, 3:30", "Ta - seeya then!". Or even just 2, Dawn: REQUEST, Tim: RESPOND (auto close), this could imply that Dawn and Tim are really close, or really not close.
BTW: We are not designing reliable messaging protocols here folks. The chat software should tell if any message was lost.