If a relation is undefined for a recored in an entity selection, it may mean the record is orphaned. A record becomes orphaned typically when the record is from the "many" table (child) and it it not linked to a record in the "one" table (parent).



When a parent record (record in "one" table) does not have any related child records (record in the "many" table), the relation for the parent record will appear as an empty entity seleciton.



For child records with an undefined relation, it must be assigned to a parent record to make the relation valid.