Compare the rule with concrete cases
Original fictional configuration has A parent B, B parent C and C as root. All may inherit value size. Proposed C parent A would produce A→B→C→A. The local model rejects parent changes that create a cycle, leaving the accepted hierarchy unchanged.
| Record | Accepted parent | Proposed parent | Decision |
|---|---|---|---|
| A | B | B | Unchanged |
| B | C | C | Unchanged |
| C | Root | A | Reject cycle |
Work through the distinction
A cyclic hierarchy is a structural invalidity, not a missing default value. Assigning an arbitrary fallback would hide the invalid parent relationship.
After rejection, what is A’s accepted chain?
Show the worked answer
A→B→C→root. The proposed C→A link was not saved.
Acceptance wording to adapt
Before saving a parent change, follow the proposed parent chain. Reject if it revisits any record, and preserve all accepted parent links. A root must terminate the chain.