id1
|
|
|---->id2
|     (1)
|      |
|------|------>id3---->id4
|      |       (1)      (2)
|      |        |        |
|      |        x        |
x      |                 |
       |                 x
       |
       |----------------------->id5
       |                        (2)
       |                         |
       |                         |
       |                         x
       |
       x