| class  | InvalidRelationIdException | This exception is raised when relation id provided for a relation is already
 used. | 
| class  | InvalidRelationServiceException | This exception is raised when an invalid Relation Service is provided. | 
| class  | InvalidRelationTypeException | Invalid relation type. | 
| class  | InvalidRoleInfoException | This exception is raised when, in a role info, its minimum degree is greater
 than its maximum degree. | 
| class  | InvalidRoleValueException | Role value is invalid. | 
| class  | RelationNotFoundException | This exception is raised when there is no relation for a given relation id
 in a Relation Service. | 
| class  | RelationServiceNotRegisteredException | This exception is raised when an access is done to the Relation Service and
 that one is not registered. | 
| class  | RelationTypeNotFoundException | This exception is raised when there is no relation type with given name in
 Relation Service. | 
| class  | RoleInfoNotFoundException | This exception is raised when there is no role info with given name in a
 given relation type. | 
| class  | RoleNotFoundException | This exception is raised when a role in a relation does not exist, or is not
 readable, or is not settable. |