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FA-45591 / Data systems / Open access

Default dependency cycles silently return a partial row · case 01

Default dependency cycles silently return a partial row.

Verified by executionVariant 1 · 7 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

default-column-dependencies: Default dependency cycles silently return a partial row.

THE FAILURE

default-column-dependencies: Default dependency cycles silently return a partial row.

Unsuccessful approach: An empty row conceals the unresolved default contract.

Case contract

Materialize missing columns using ordered default rules [target,source-or-None,constant]. A constant rule writes constant; a dependent rule writes source+constant, propagating explicit null. Existing columns including None and zero never change. Resolve forward dependencies to a fixed point; unresolved dependencies return DEFAULT_CYCLE.

Why this case matters

A bounded deterministic data engine model makes representation and changelog faults reproducible.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(d):
    try:
        row,rules=d
        result=dict(row)
        pending=[rule for rule in rules if rule[0] not in result]
        while pending:
            progressed=False; later=[]
            for target,source,constant in pending:
                if source is not None and source not in result:
                    later.append([target,source,constant]); continue
                result[target]=constant if source is None else (None if result[source] is None else result[source]+constant)
                progressed=True
            if not progressed: return result
            pending=later
        return result
    except (IndexError, KeyError, ValueError, StopIteration) as exc:
        return {"representation_error": type(exc).__name__}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
if N == 1:
    check('forward dependency', solve([{}, [['b', 'a', 2], ['a', None, 1]]]), {'a': 1, 'b': 3})
    check('explicit null', solve([{'a': None}, [['a', None, 1], ['b', 'a', 1]]]), {'a': None, 'b': None})
    check('explicit zero', solve([{'a': 0}, [['a', None, 1], ['b', 'a', 2]]]), {'a': 0, 'b': 2})
    check('dependency cycle', solve([{}, [['a', 'b', 1], ['b', 'a', 1]]]), 'DEFAULT_CYCLE')
    check('provided unrelated', solve([{'x': 1}, [['a', None, 2]]]), {'x': 1, 'a': 2})
    check('source provided', solve([{'a': 1}, [['b', 'a', 3]]]), {'a': 1, 'b': 4})
    check('no defaults', solve([{'a': 1}, []]), {'a': 1})
elif N == 2:
    check('forward dependency', solve([{}, [['b', 'a', 2], ['a', None, 2]]]), {'a': 2, 'b': 4})
    check('explicit null', solve([{'a': None}, [['a', None, 2], ['b', 'a', 1]]]), {'a': None, 'b': None})
    check('explicit zero', solve([{'a': 0}, [['a', None, 2], ['b', 'a', 2]]]), {'a': 0, 'b': 2})
    check('dependency cycle', solve([{}, [['a', 'b', 1], ['b', 'a', 1]]]), 'DEFAULT_CYCLE')
    check('provided unrelated', solve([{'x': 2}, [['a', None, 3]]]), {'x': 2, 'a': 3})
    check('source provided', solve([{'a': 2}, [['b', 'a', 3]]]), {'a': 2, 'b': 5})
    check('no defaults', solve([{'a': 2}, []]), {'a': 2})
elif N == 3:
    check('forward dependency', solve([{}, [['b', 'a', 2], ['a', None, 3]]]), {'a': 3, 'b': 5})
    check('explicit null', solve([{'a': None}, [['a', None, 3], ['b', 'a', 1]]]), {'a': None, 'b': None})
    check('explicit zero', solve([{'a': 0}, [['a', None, 3], ['b', 'a', 2]]]), {'a': 0, 'b': 2})
    check('dependency cycle', solve([{}, [['a', 'b', 1], ['b', 'a', 1]]]), 'DEFAULT_CYCLE')
    check('provided unrelated', solve([{'x': 3}, [['a', None, 4]]]), {'x': 3, 'a': 4})
    check('source provided', solve([{'a': 3}, [['b', 'a', 3]]]), {'a': 3, 'b': 6})
    check('no defaults', solve([{'a': 3}, []]), {'a': 3})
elif N == 4:
    check('forward dependency', solve([{}, [['b', 'a', 2], ['a', None, 4]]]), {'a': 4, 'b': 6})
    check('explicit null', solve([{'a': None}, [['a', None, 4], ['b', 'a', 1]]]), {'a': None, 'b': None})
    check('explicit zero', solve([{'a': 0}, [['a', None, 4], ['b', 'a', 2]]]), {'a': 0, 'b': 2})
    check('dependency cycle', solve([{}, [['a', 'b', 1], ['b', 'a', 1]]]), 'DEFAULT_CYCLE')
    check('provided unrelated', solve([{'x': 4}, [['a', None, 5]]]), {'x': 4, 'a': 5})
    check('source provided', solve([{'a': 4}, [['b', 'a', 3]]]), {'a': 4, 'b': 7})
    check('no defaults', solve([{'a': 4}, []]), {'a': 4})
elif N == 5:
    check('forward dependency', solve([{}, [['b', 'a', 2], ['a', None, 5]]]), {'a': 5, 'b': 7})
    check('explicit null', solve([{'a': None}, [['a', None, 5], ['b', 'a', 1]]]), {'a': None, 'b': None})
    check('explicit zero', solve([{'a': 0}, [['a', None, 5], ['b', 'a', 2]]]), {'a': 0, 'b': 2})
    check('dependency cycle', solve([{}, [['a', 'b', 1], ['b', 'a', 1]]]), 'DEFAULT_CYCLE')
    check('provided unrelated', solve([{'x': 5}, [['a', None, 6]]]), {'x': 5, 'a': 6})
    check('source provided', solve([{'a': 5}, [['b', 'a', 3]]]), {'a': 5, 'b': 8})
    check('no defaults', solve([{'a': 5}, []]), {'a': 5})
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
forward dependency{'a': 1, 'b': 3}{'a': 1, 'b': 3}Passed
explicit null{'a': None, 'b': None}{'a': None, 'b': None}Passed
explicit zero{'a': 0, 'b': 2}{'a': 0, 'b': 2}Passed
dependency cycle{}DEFAULT_CYCLEFailed
provided unrelated{'a': 2, 'x': 1}{'a': 2, 'x': 1}Passed
source provided{'a': 1, 'b': 4}{'a': 1, 'b': 4}Passed
no defaults{'a': 1}{'a': 1}Passed

SHA-256 / 28d2382ef841fad62fe292e560c7a07c47c66e0b9234193d72d1838234a294f1

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(d):
    try:
        row,rules=d
        result=dict(row)
        pending=[rule for rule in rules if rule[0] not in result]
        while pending:
            progressed=False; later=[]
            for target,source,constant in pending:
                if source is not None and source not in result:
                    later.append([target,source,constant]); continue
                result[target]=constant if source is None else (None if result[source] is None else result[source]+constant)
                progressed=True
            if not progressed: return {}
            pending=later
        return result
    except (IndexError, KeyError, ValueError, StopIteration) as exc:
        return {"representation_error": type(exc).__name__}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
if N == 1:
    check('forward dependency', solve([{}, [['b', 'a', 2], ['a', None, 1]]]), {'a': 1, 'b': 3})
    check('explicit null', solve([{'a': None}, [['a', None, 1], ['b', 'a', 1]]]), {'a': None, 'b': None})
    check('explicit zero', solve([{'a': 0}, [['a', None, 1], ['b', 'a', 2]]]), {'a': 0, 'b': 2})
    check('dependency cycle', solve([{}, [['a', 'b', 1], ['b', 'a', 1]]]), 'DEFAULT_CYCLE')
    check('provided unrelated', solve([{'x': 1}, [['a', None, 2]]]), {'x': 1, 'a': 2})
    check('source provided', solve([{'a': 1}, [['b', 'a', 3]]]), {'a': 1, 'b': 4})
    check('no defaults', solve([{'a': 1}, []]), {'a': 1})
elif N == 2:
    check('forward dependency', solve([{}, [['b', 'a', 2], ['a', None, 2]]]), {'a': 2, 'b': 4})
    check('explicit null', solve([{'a': None}, [['a', None, 2], ['b', 'a', 1]]]), {'a': None, 'b': None})
    check('explicit zero', solve([{'a': 0}, [['a', None, 2], ['b', 'a', 2]]]), {'a': 0, 'b': 2})
    check('dependency cycle', solve([{}, [['a', 'b', 1], ['b', 'a', 1]]]), 'DEFAULT_CYCLE')
    check('provided unrelated', solve([{'x': 2}, [['a', None, 3]]]), {'x': 2, 'a': 3})
    check('source provided', solve([{'a': 2}, [['b', 'a', 3]]]), {'a': 2, 'b': 5})
    check('no defaults', solve([{'a': 2}, []]), {'a': 2})
elif N == 3:
    check('forward dependency', solve([{}, [['b', 'a', 2], ['a', None, 3]]]), {'a': 3, 'b': 5})
    check('explicit null', solve([{'a': None}, [['a', None, 3], ['b', 'a', 1]]]), {'a': None, 'b': None})
    check('explicit zero', solve([{'a': 0}, [['a', None, 3], ['b', 'a', 2]]]), {'a': 0, 'b': 2})
    check('dependency cycle', solve([{}, [['a', 'b', 1], ['b', 'a', 1]]]), 'DEFAULT_CYCLE')
    check('provided unrelated', solve([{'x': 3}, [['a', None, 4]]]), {'x': 3, 'a': 4})
    check('source provided', solve([{'a': 3}, [['b', 'a', 3]]]), {'a': 3, 'b': 6})
    check('no defaults', solve([{'a': 3}, []]), {'a': 3})
elif N == 4:
    check('forward dependency', solve([{}, [['b', 'a', 2], ['a', None, 4]]]), {'a': 4, 'b': 6})
    check('explicit null', solve([{'a': None}, [['a', None, 4], ['b', 'a', 1]]]), {'a': None, 'b': None})
    check('explicit zero', solve([{'a': 0}, [['a', None, 4], ['b', 'a', 2]]]), {'a': 0, 'b': 2})
    check('dependency cycle', solve([{}, [['a', 'b', 1], ['b', 'a', 1]]]), 'DEFAULT_CYCLE')
    check('provided unrelated', solve([{'x': 4}, [['a', None, 5]]]), {'x': 4, 'a': 5})
    check('source provided', solve([{'a': 4}, [['b', 'a', 3]]]), {'a': 4, 'b': 7})
    check('no defaults', solve([{'a': 4}, []]), {'a': 4})
elif N == 5:
    check('forward dependency', solve([{}, [['b', 'a', 2], ['a', None, 5]]]), {'a': 5, 'b': 7})
    check('explicit null', solve([{'a': None}, [['a', None, 5], ['b', 'a', 1]]]), {'a': None, 'b': None})
    check('explicit zero', solve([{'a': 0}, [['a', None, 5], ['b', 'a', 2]]]), {'a': 0, 'b': 2})
    check('dependency cycle', solve([{}, [['a', 'b', 1], ['b', 'a', 1]]]), 'DEFAULT_CYCLE')
    check('provided unrelated', solve([{'x': 5}, [['a', None, 6]]]), {'x': 5, 'a': 6})
    check('source provided', solve([{'a': 5}, [['b', 'a', 3]]]), {'a': 5, 'b': 8})
    check('no defaults', solve([{'a': 5}, []]), {'a': 5})
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
forward dependency{'a': 1, 'b': 3}{'a': 1, 'b': 3}Passed
explicit null{'a': None, 'b': None}{'a': None, 'b': None}Passed
explicit zero{'a': 0, 'b': 2}{'a': 0, 'b': 2}Passed
dependency cycle{}DEFAULT_CYCLEFailed
provided unrelated{'a': 2, 'x': 1}{'a': 2, 'x': 1}Passed
source provided{'a': 1, 'b': 4}{'a': 1, 'b': 4}Passed
no defaults{'a': 1}{'a': 1}Passed

SHA-256 / 346570c713e17981e1925a9c025bfd12b84204913c3a970e1d4e497266c0933d

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 7 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

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Verification & scope

Offline stipulated semantics over valid small inputs; no performance, concurrency, or production-engine conformance claim. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:44:23.812041+00:00.

Case digest / 26864fd9065eb0ea0b56a690aeeea02f8a3ae2b42fa0d73717277eeb45c23886