Each TISSUE
| K | must be related to one or more CELL |
| may be NULL one or more PERSON ORGAN | |
| may be related to one or more TISSUE CARE ACTIVITY | |
| may be related to one and only one TISSUE TRANSPLANT |
Classes
| K | must be related to one or more CELL |
| may be NULL one or more PERSON ORGAN | |
| may be related to one or more TISSUE CARE ACTIVITY | |
| may be related to one and only one TISSUE TRANSPLANT |