{"abstract":"Correct ISBNs are rejected and some typos are accepted.","category":"Check-digit algorithms","checks":8,"contract":"ISBN-10 validation. Hyphens and spaces are removed; the rest must be nine ASCII digits followed by a digit or uppercase X (value 10), else \"malformed\". Weights run 10 down to 1 from the left and the number is \"valid\" when the weighted sum is divisible by 11, else \"invalid\".","evaluation_group":"w2-check_digit_algorithms-isbn10-validate","failed_approach":"Using 11 - i adds an unweighted digit sum to the total and still fails the mod-11 test.","family":"w2-check_digit_algorithms-isbn10-validate-position-weight","id":"FA-72421","implementations":{"attempt":{"sha256":"f5916e580b2f66c521d660d39a1dd879980ea0b4a2bfe4b00505a1654a6043e3","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(s):\n    t = s.replace('-', '').replace(' ', '')\n    if len(t) != 10 or not t.isascii() or not t[:9].isdigit():\n        return 'malformed'\n    if not (t[9].isdigit() or t[9] == 'X'):\n        return 'malformed'\n    total = 0\n    for i, ch in enumerate(t):\n        v = 10 if ch == 'X' else int(ch)\n        total += (11 - i) * v\n    return 'valid' if total % 11 == 0 else 'invalid'\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[['regression [\"5892872939\"]', ['5892872939'], 'valid'], ['regression [\"2399553950\"]', ['2399553950'], 'valid'], ['control [\"9465545449\"]', ['9465545449'], 'valid'], ['control [\"2266685686\"]', ['2266685686'], 'valid'], ['control [\"0000000000\"]', ['0000000000'], 'valid'], ['control [\"123456789X\"]', ['123456789X'], 'valid'], ['control [\"2399553951\"]', ['2399553951'], 'invalid'], ['control [\"8292844660\"]', ['8292844660'], 'invalid']], [['regression [\"9379774826\"]', ['9379774826'], 'valid'], ['regression [\"2892681790\"]', ['2892681790'], 'valid'], ['control [\"8292844660\"]', ['8292844660'], 'invalid'], ['control [\"9379774827\"]', ['9379774827'], 'invalid'], ['control [\"2892681791\"]', ['2892681791'], 'invalid'], ['control [\"5900307906\"]', ['5900307906'], 'invalid'], ['control [\"9-465-54544-9\"]', ['9-465-54544-9'], 'valid'], ['control [\"2-266-68568-6\"]', ['2-266-68568-6'], 'valid']], [['regression [\"3905987139\"]', ['3905987139'], 'valid'], ['regression [\"7113753523\"]', ['7113753523'], 'valid'], ['control [\"2-266-68568-6\"]', ['2-266-68568-6'], 'valid'], ['control [\"5892872938\"]', ['5892872938'], 'invalid'], ['control [\"8292844669\"]', ['8292844669'], 'invalid'], ['control [\"9379774825\"]', ['9379774825'], 'invalid'], ['control [\"5900307904\"]', ['5900307904'], 'invalid'], ['control [\"0306406153\"]', ['0306406153'], 'invalid']], [['regression [\"3407375115\"]', ['3407375115'], 'valid'], ['regression [\"8449627923\"]', ['8449627923'], 'valid'], ['control [\"0306406153\"]', ['0306406153'], 'invalid'], ['control [\"03064061\"]', ['03064061'], 'malformed'], ['control [\"030640615X1\"]', ['030640615X1'], 'malformed'], ['control [\"0306406X52\"]', ['0306406X52'], 'malformed'], ['control [\"9465545449\"]', ['9465545449'], 'valid'], ['control [\"2266685686\"]', ['2266685686'], 'valid']], [['regression [\"080442957X\"]', ['080442957X'], 'valid'], ['regression [\"0306406152\"]', ['0306406152'], 'valid'], ['control [\"2266685686\"]', ['2266685686'], 'valid'], ['control [\"0000000000\"]', ['0000000000'], 'valid'], ['control [\"123456789X\"]', ['123456789X'], 'valid'], ['control [\"2399553951\"]', ['2399553951'], 'invalid'], ['control [\"8292844660\"]', ['8292844660'], 'invalid'], ['control [\"9379774827\"]', ['9379774827'], 'invalid']]]\nfor label, args, expected in fixtures[N - 1]:\n    check(label, solve(*args), expected)\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":"6a619d10468e6eb296f168069aa3d39b2a1d63f377275bdff6b4c3ce61867cbf","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(s):\n    t = s.replace('-', '').replace(' ', '')\n    if len(t) != 10 or not t.isascii() or not t[:9].isdigit():\n        return 'malformed'\n    if not (t[9].isdigit() or t[9] == 'X'):\n        return 'malformed'\n    total = 0\n    for i, ch in enumerate(t):\n        v = 10 if ch == 'X' else int(ch)\n        total += (9 - i) * v\n    return 'valid' if total % 11 == 0 else 'invalid'\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[['regression [\"5892872939\"]', ['5892872939'], 'valid'], ['regression [\"2399553950\"]', ['2399553950'], 'valid'], ['control [\"9465545449\"]', ['9465545449'], 'valid'], ['control [\"2266685686\"]', ['2266685686'], 'valid'], ['control [\"0000000000\"]', ['0000000000'], 'valid'], ['control [\"123456789X\"]', ['123456789X'], 'valid'], ['control [\"2399553951\"]', ['2399553951'], 'invalid'], ['control [\"8292844660\"]', ['8292844660'], 'invalid']], [['regression [\"9379774826\"]', ['9379774826'], 'valid'], ['regression [\"2892681790\"]', ['2892681790'], 'valid'], ['control [\"8292844660\"]', ['8292844660'], 'invalid'], ['control [\"9379774827\"]', ['9379774827'], 'invalid'], ['control [\"2892681791\"]', ['2892681791'], 'invalid'], ['control [\"5900307906\"]', ['5900307906'], 'invalid'], ['control [\"9-465-54544-9\"]', ['9-465-54544-9'], 'valid'], ['control [\"2-266-68568-6\"]', ['2-266-68568-6'], 'valid']], [['regression [\"3905987139\"]', ['3905987139'], 'valid'], ['regression [\"7113753523\"]', ['7113753523'], 'valid'], ['control [\"2-266-68568-6\"]', ['2-266-68568-6'], 'valid'], ['control [\"5892872938\"]', ['5892872938'], 'invalid'], ['control [\"8292844669\"]', ['8292844669'], 'invalid'], ['control [\"9379774825\"]', ['9379774825'], 'invalid'], ['control [\"5900307904\"]', ['5900307904'], 'invalid'], ['control [\"0306406153\"]', ['0306406153'], 'invalid']], [['regression [\"3407375115\"]', ['3407375115'], 'valid'], ['regression [\"8449627923\"]', ['8449627923'], 'valid'], ['control [\"0306406153\"]', ['0306406153'], 'invalid'], ['control [\"03064061\"]', ['03064061'], 'malformed'], ['control [\"030640615X1\"]', ['030640615X1'], 'malformed'], ['control [\"0306406X52\"]', ['0306406X52'], 'malformed'], ['control [\"9465545449\"]', ['9465545449'], 'valid'], ['control [\"2266685686\"]', ['2266685686'], 'valid']], [['regression [\"080442957X\"]', ['080442957X'], 'valid'], ['regression [\"0306406152\"]', ['0306406152'], 'valid'], ['control [\"2266685686\"]', ['2266685686'], 'valid'], ['control [\"0000000000\"]', ['0000000000'], 'valid'], ['control [\"123456789X\"]', ['123456789X'], 'valid'], ['control [\"2399553951\"]', ['2399553951'], 'invalid'], ['control [\"8292844660\"]', ['8292844660'], 'invalid'], ['control [\"9379774827\"]', ['9379774827'], 'invalid']]]\nfor label, args, expected in fixtures[N - 1]:\n    check(label, solve(*args), expected)\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"},"fixed":{"sha256":"a6bbe916da7da4c180843518e2965d632fecb3a695552e014ff900a02ec29034","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(s):\n    t = s.replace('-', '').replace(' ', '')\n    if len(t) != 10 or not t.isascii() or not t[:9].isdigit():\n        return 'malformed'\n    if not (t[9].isdigit() or t[9] == 'X'):\n        return 'malformed'\n    total = 0\n    for i, ch in enumerate(t):\n        v = 10 if ch == 'X' else int(ch)\n        total += (10 - i) * v\n    return 'valid' if total % 11 == 0 else 'invalid'\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nfixtures = [[['regression [\"5892872939\"]', ['5892872939'], 'valid'], ['regression [\"2399553950\"]', ['2399553950'], 'valid'], ['control [\"9465545449\"]', ['9465545449'], 'valid'], ['control [\"2266685686\"]', ['2266685686'], 'valid'], ['control [\"0000000000\"]', ['0000000000'], 'valid'], ['control [\"123456789X\"]', ['123456789X'], 'valid'], ['control [\"2399553951\"]', ['2399553951'], 'invalid'], ['control [\"8292844660\"]', ['8292844660'], 'invalid']], [['regression [\"9379774826\"]', ['9379774826'], 'valid'], ['regression [\"2892681790\"]', ['2892681790'], 'valid'], ['control [\"8292844660\"]', ['8292844660'], 'invalid'], ['control [\"9379774827\"]', ['9379774827'], 'invalid'], ['control [\"2892681791\"]', ['2892681791'], 'invalid'], ['control [\"5900307906\"]', ['5900307906'], 'invalid'], ['control [\"9-465-54544-9\"]', ['9-465-54544-9'], 'valid'], ['control [\"2-266-68568-6\"]', ['2-266-68568-6'], 'valid']], [['regression [\"3905987139\"]', ['3905987139'], 'valid'], ['regression [\"7113753523\"]', ['7113753523'], 'valid'], ['control [\"2-266-68568-6\"]', ['2-266-68568-6'], 'valid'], ['control [\"5892872938\"]', ['5892872938'], 'invalid'], ['control [\"8292844669\"]', ['8292844669'], 'invalid'], ['control [\"9379774825\"]', ['9379774825'], 'invalid'], ['control [\"5900307904\"]', ['5900307904'], 'invalid'], ['control [\"0306406153\"]', ['0306406153'], 'invalid']], [['regression [\"3407375115\"]', ['3407375115'], 'valid'], ['regression [\"8449627923\"]', ['8449627923'], 'valid'], ['control [\"0306406153\"]', ['0306406153'], 'invalid'], ['control [\"03064061\"]', ['03064061'], 'malformed'], ['control [\"030640615X1\"]', ['030640615X1'], 'malformed'], ['control [\"0306406X52\"]', ['0306406X52'], 'malformed'], ['control [\"9465545449\"]', ['9465545449'], 'valid'], ['control [\"2266685686\"]', ['2266685686'], 'valid']], [['regression [\"080442957X\"]', ['080442957X'], 'valid'], ['regression [\"0306406152\"]', ['0306406152'], 'valid'], ['control [\"2266685686\"]', ['2266685686'], 'valid'], ['control [\"0000000000\"]', ['0000000000'], 'valid'], ['control [\"123456789X\"]', ['123456789X'], 'valid'], ['control [\"2399553951\"]', ['2399553951'], 'invalid'], ['control [\"8292844660\"]', ['8292844660'], 'invalid'], ['control [\"9379774827\"]', ['9379774827'], 'invalid']]]\nfor label, args, expected in fixtures[N - 1]:\n    check(label, solve(*args), expected)\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":"A deterministic, bounded teaching model of the named scheme under the stated contract; not a certified validator. 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":"w2-check_digit_algorithms-isbn10-validate-position-weight","generated_at":"2026-09-29T14:48:38.430764+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Catalogue and bookstore systems validate legacy ISBN-10 identifiers on intake.","repair":"Weight position i (from the left, 0-based) by 10 - i.","root_cause":"The weight is 9 - i, so the check character gets weight 0 and every other weight is one short.","sha256":"2fac6e6915cf633b6448b66363046a157b83cfa3159f29a9c36ca5b0a85493cb","title":"ISBN-10 weights start at nine · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":37.129,"exit_code":1,"observations":[{"actual":"invalid","check":"regression [\"5892872939\"]","expected":"valid","passed":false},{"actual":"invalid","check":"regression [\"2399553950\"]","expected":"valid","passed":false},{"actual":"valid","check":"control [\"9465545449\"]","expected":"valid","passed":true},{"actual":"valid","check":"control [\"2266685686\"]","expected":"valid","passed":true},{"actual":"valid","check":"control [\"0000000000\"]","expected":"valid","passed":true},{"actual":"valid","check":"control [\"123456789X\"]","expected":"valid","passed":true},{"actual":"invalid","check":"control [\"2399553951\"]","expected":"invalid","passed":true},{"actual":"invalid","check":"control [\"8292844660\"]","expected":"invalid","passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"regression [\\\"5892872939\\\"]\", \"actual\": \"invalid\", \"expected\": \"valid\", \"passed\": false}, {\"check\": \"regression [\\\"2399553950\\\"]\", \"actual\": \"invalid\", \"expected\": \"valid\", \"passed\": false}, {\"check\": \"control [\\\"9465545449\\\"]\", \"actual\": \"valid\", \"expected\": \"valid\", \"passed\": true}, {\"check\": \"control [\\\"2266685686\\\"]\", \"actual\": \"valid\", \"expected\": \"valid\", \"passed\": true}, {\"check\": \"control [\\\"0000000000\\\"]\", \"actual\": \"valid\", \"expected\": \"valid\", \"passed\": true}, {\"check\": \"control [\\\"123456789X\\\"]\", \"actual\": \"valid\", \"expected\": \"valid\", \"passed\": true}, {\"check\": \"control [\\\"2399553951\\\"]\", \"actual\": \"invalid\", \"expected\": \"invalid\", \"passed\": true}, {\"check\": \"control [\\\"8292844660\\\"]\", \"actual\": \"invalid\", \"expected\": \"invalid\", \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":39.749,"exit_code":1,"observations":[{"actual":"invalid","check":"regression [\"5892872939\"]","expected":"valid","passed":false},{"actual":"invalid","check":"regression [\"2399553950\"]","expected":"valid","passed":false},{"actual":"valid","check":"control [\"9465545449\"]","expected":"valid","passed":true},{"actual":"valid","check":"control [\"2266685686\"]","expected":"valid","passed":true},{"actual":"valid","check":"control [\"0000000000\"]","expected":"valid","passed":true},{"actual":"valid","check":"control [\"123456789X\"]","expected":"valid","passed":true},{"actual":"invalid","check":"control [\"2399553951\"]","expected":"invalid","passed":true},{"actual":"invalid","check":"control [\"8292844660\"]","expected":"invalid","passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"regression [\\\"5892872939\\\"]\", \"actual\": \"invalid\", \"expected\": \"valid\", \"passed\": false}, {\"check\": \"regression [\\\"2399553950\\\"]\", \"actual\": \"invalid\", \"expected\": \"valid\", \"passed\": false}, {\"check\": \"control [\\\"9465545449\\\"]\", \"actual\": \"valid\", \"expected\": \"valid\", \"passed\": true}, {\"check\": \"control [\\\"2266685686\\\"]\", \"actual\": \"valid\", \"expected\": \"valid\", \"passed\": true}, {\"check\": \"control [\\\"0000000000\\\"]\", \"actual\": \"valid\", \"expected\": \"valid\", \"passed\": true}, {\"check\": \"control [\\\"123456789X\\\"]\", \"actual\": \"valid\", \"expected\": \"valid\", \"passed\": true}, {\"check\": \"control [\\\"2399553951\\\"]\", \"actual\": \"invalid\", \"expected\": \"invalid\", \"passed\": true}, {\"check\": \"control [\\\"8292844660\\\"]\", \"actual\": \"invalid\", \"expected\": \"invalid\", \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":39.148,"exit_code":0,"observations":[{"actual":"valid","check":"regression [\"5892872939\"]","expected":"valid","passed":true},{"actual":"valid","check":"regression [\"2399553950\"]","expected":"valid","passed":true},{"actual":"valid","check":"control [\"9465545449\"]","expected":"valid","passed":true},{"actual":"valid","check":"control [\"2266685686\"]","expected":"valid","passed":true},{"actual":"valid","check":"control [\"0000000000\"]","expected":"valid","passed":true},{"actual":"valid","check":"control [\"123456789X\"]","expected":"valid","passed":true},{"actual":"invalid","check":"control [\"2399553951\"]","expected":"invalid","passed":true},{"actual":"invalid","check":"control [\"8292844660\"]","expected":"invalid","passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"regression [\\\"5892872939\\\"]\", \"actual\": \"valid\", \"expected\": \"valid\", \"passed\": true}, {\"check\": \"regression [\\\"2399553950\\\"]\", \"actual\": \"valid\", \"expected\": \"valid\", \"passed\": true}, {\"check\": \"control [\\\"9465545449\\\"]\", \"actual\": \"valid\", \"expected\": \"valid\", \"passed\": true}, {\"check\": \"control [\\\"2266685686\\\"]\", \"actual\": \"valid\", \"expected\": \"valid\", \"passed\": true}, {\"check\": \"control [\\\"0000000000\\\"]\", \"actual\": \"valid\", \"expected\": \"valid\", \"passed\": true}, {\"check\": \"control [\\\"123456789X\\\"]\", \"actual\": \"valid\", \"expected\": \"valid\", \"passed\": true}, {\"check\": \"control [\\\"2399553951\\\"]\", \"actual\": \"invalid\", \"expected\": \"invalid\", \"passed\": true}, {\"check\": \"control [\\\"8292844660\\\"]\", \"actual\": \"invalid\", \"expected\": \"invalid\", \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}