| 1 | Parent |
| A code to indicate a parent relationship. |
| 2 | Child |
| A code to indicate a child relationship. |
| 3 | Peer, internal |
| A code to indicate an internal peer relationship. |
| 4 | Peer, external |
| A code to indicate an external peer relationship. |
| 5 | Finish to start constraint |
| A code to indicate a finish to start constraint relationship. |
| 6 | Start to start constraint |
| A code to indicate a start to start constraint relationship. |
| 7 | Finish to finish constraint |
| A code to indicate a finish to finish constraint relationship. |
| 8 | Start to finish constraint |
| A code to indicate a start to finish constraint relationship. |
| 9 | Owner |
| A code to indicate an owner relationship. |
| 10 | Contact |
| A code to indicate a contact relationship. |
| 11 | Spouse |
| A code to indicate a spouse relationship. |
| 12 | Sibling |
| A code to indicate the relationship between brothers and/or sisters. |
| 13 | Father |
| A code to indicate a father relationship. |
| 14 | Mother |
| A code to indicate a mother relationship. |
| 15 | Neighbour |
| A code to indicate a neighbour relationship. |
| 16 | Friend |
| A code to indicate a friend relationship. |
| 17 | Guardian |
| A code to indicate a guardian relationship. |
| 18 | Connecting to |
| The specified object connects to the related object. |
