|
| 可达集 | 前因集 | 层级 |
| S1 | 1 | 1 2 3 4 5 7 8 9 | L1 |
| S2 | 1 2 | 2 3 4 5 7 8 9 | L2 |
| S3 | 1 2 3 4 | 3 4 5 8 9 | L3 |
| S4 | 1 2 3 4 | 3 4 5 8 9 | L3 |
| S5 | 1 2 3 4 5 6 | 5 9 | L4 |
| S6 | 6 | 5 6 7 8 9 | L1 |
| S7 | 1 2 6 7 | 7 9 | L3 |
| S8 | 1 2 3 4 6 8 | 8 9 | L4 |
| S9 | 1 2 3 4 5 6 7 8 9 | 9 | L5 |