| ERROR | type of supertype attribute string can not be a subtype or reference to a subtype in this release |
| CAUSE | User tried to complete a type, Tsub as a subtype of another type, Tsuper where Tsuper contained an attribute of type Tsub or of type REF to Tsub. This is an implementation restriction. |
| ACTION | Change the design of code to not use any type with attribute whose type is of subtype or REF to subtype. |