Errors block the transition to the refinement phase, whereas warnings highlight incomplete parts without halting the process.
Rule violations
| Message | How to fix it |
|---|
| The entity has no identifier | Mark at least one attribute as Identifier. |
| A child entity must not have any identifier | Remove it; the child uses the parent’s identifier. |
| The relationship must have at least two participations | Use Connect to link a second entity. |
| A recursive relationship requires participation roles | Set a Role on both participations. |
| A ternary relationship requires all participation cardinalities to have maximum value N | Set every participation to (0,N) or (1,N). |
| A time entity must have only identifier attributes | Remove the non-identifier attributes or move them to the relationship. |
| A time entity must participate with a minimum cardinality of 1 | Set the participations to (1,N). |
Naming conflicts
| Message | How to fix it |
|---|
| There is a name conflict | Two entities or relationships share a name. Rename one. |
| Multiple attributes with the same name | Rename the duplicate attribute or subattribute. |
Warnings
| Message | What to check |
|---|
| The entity has no attributes (apart from identifiers) | Whether something is missing. |
| Embedding an optional entity may lead to data loss | Whether a reference fits better. |