{"abstract":"one group appears on both sides.","category":"Dataset split isolation","checks":6,"contract":"Rows are [id,group]. Return IDs assigned to train under the supplied group->side map; unknown groups are validation.","contract_signature":"rows, sides","evaluation_group":"ds-group-projection","failed_approach":"The repair forces the first row into training even when its group is mapped to validation.","family":"w3-dataset-split-isolation-group-side-consistency","id":"FA-97841","implementations":{"attempt":{"sha256":"a3d387e254531d13bb596cb7a9ba69aeebf71679010c35fab7a5ecebbd5a90ca","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(rows, sides):\n    return [i for i,g in rows if sides.get(g,'validation')=='train' or i==rows[0][0]]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('same group',solve([['a','g'],['b','g']],{'g':'train'}),['a','b'])\ncheck('validation group',solve([['a','h']],{'h':'validation'}),[])\ncheck('unknown defaults validation',solve([['a','z']],{}),[])\ncheck('interleaved groups',solve([['a','g'],['b','h'],['c','g']],{'g':'train','h':'validation'}),['a','c'])\ncheck('empty',solve([] ,{'g':'train'}),[])\ncheck('singleton train',solve([['x','g']],{'g':'train'}),['x'])\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"broken":{"sha256":"57b4af207308f53e4c5fee25dcc8ab28b91d91e8017d76e8aa207a81bc634887","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(rows, sides):\n    return [i for j,(i,g) in enumerate(rows) if sides.get(g,'validation')=='train' and j%2==0]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('same group',solve([['a','g'],['b','g']],{'g':'train'}),['a','b'])\ncheck('validation group',solve([['a','h']],{'h':'validation'}),[])\ncheck('unknown defaults validation',solve([['a','z']],{}),[])\ncheck('interleaved groups',solve([['a','g'],['b','h'],['c','g']],{'g':'train','h':'validation'}),['a','c'])\ncheck('empty',solve([] ,{'g':'train'}),[])\ncheck('singleton train',solve([['x','g']],{'g':'train'}),['x'])\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"}},"limitations":"Inputs are small in-memory records with self-contained contracts; no claim is made about production sampling quality. 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.","method":"Deterministic executable model with adversarial boundary fixtures.","provenance":{"created_by":"Failure Map","dependencies":"Python standard library","family":"w3-dataset-split-isolation-group-side-consistency","generated_at":"2026-09-30T16:48:06.689096+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"This toy split allocator makes membership rules explicit for reproducible evaluation fixtures.","root_cause":"The implementation uses row position to decide which mapped-train rows enter training, so members of one group can land on different sides.","sha256":"66ecb4d0a0eaabdf571eb61931591470c32c9b00f96ee8f0570b58085aa29c60","title":"Dataset split: one group appears on both sides · case 01","variant":1,"variant_policy":"The same explicitly authored fixtures repeat across all five numbered records; runtime N is unused. These records share one mechanism and must remain together in evaluation splits.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":27.691,"exit_code":1,"observations":[{"actual":["a","b"],"check":"same group","expected":["a","b"],"passed":true},{"actual":["a"],"check":"validation group","expected":[],"passed":false},{"actual":["a"],"check":"unknown defaults validation","expected":[],"passed":false},{"actual":["a","c"],"check":"interleaved groups","expected":["a","c"],"passed":true},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":["x"],"check":"singleton train","expected":["x"],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"same group\", \"actual\": [\"a\", \"b\"], \"expected\": [\"a\", \"b\"], \"passed\": true}, {\"check\": \"validation group\", \"actual\": [\"a\"], \"expected\": [], \"passed\": false}, {\"check\": \"unknown defaults validation\", \"actual\": [\"a\"], \"expected\": [], \"passed\": false}, {\"check\": \"interleaved groups\", \"actual\": [\"a\", \"c\"], \"expected\": [\"a\", \"c\"], \"passed\": true}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"singleton train\", \"actual\": [\"x\"], \"expected\": [\"x\"], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":33.208,"exit_code":1,"observations":[{"actual":["a"],"check":"same group","expected":["a","b"],"passed":false},{"actual":[],"check":"validation group","expected":[],"passed":true},{"actual":[],"check":"unknown defaults validation","expected":[],"passed":true},{"actual":["a","c"],"check":"interleaved groups","expected":["a","c"],"passed":true},{"actual":[],"check":"empty","expected":[],"passed":true},{"actual":["x"],"check":"singleton train","expected":["x"],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"same group\", \"actual\": [\"a\"], \"expected\": [\"a\", \"b\"], \"passed\": false}, {\"check\": \"validation group\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"unknown defaults validation\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"interleaved groups\", \"actual\": [\"a\", \"c\"], \"expected\": [\"a\", \"c\"], \"passed\": true}, {\"check\": \"empty\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"singleton train\", \"actual\": [\"x\"], \"expected\": [\"x\"], \"passed\": true}], \"passed\": false}\n"}},"member_only":{"stages":["fixed"],"fields":["implementations.fixed","verification.fixed","harness","repair"],"note":"The verified repair, its recorded checks, the repair description, and the scoring harness are available to members."}}