{
  "site": "https://kyliandegroot.com",
  "author": "Kylian de Groot",
  "updated": "2026-08-15T10:52:42.525Z",
  "count": 2,
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    {
      "slug": "2026-absence-of-errors-is-not-evidence-of-completeness",
      "title": "Absence of Errors Is Not Evidence of Completeness",
      "subtitle": "Six elementary questions that a fiscal product cannot leave implicit when a webshop is a source",
      "year": 2026,
      "type": "paper",
      "typeLabel": "working paper",
      "authors": [
        "Kylian de Groot"
      ],
      "abstract": "A fiscal product that books webshop revenue without a human watching the feed has to answer a question that looks too simple to write down: how do we know that what arrived is everything that happened? The usual answer is operational. The webhooks are green. The sync has run for weeks. The error log is empty. That answer is not a proof. It is the claim that completeness is observable from the stream itself. It is not. A missing delivery leaves no hole in the observation. It leaves nothing. The empty error log is consistent with a complete feed and with a dropped feed. Those two worlds are indistinguishable to the receiver. A product that treats them as the same world will produce a ledger that looks finished while it is not. The merchant notices. The product does not. This paper states six questions and answers each by arithmetic on finite sets of integer cents and integer identifiers. The answers are: a push stream cannot prove its own completeness; the proof is a source-side closed statement reproduced locally; the hardest such statement is a payout that also appears on the bank; a monotone identifier makes a gap nameable within one reconciliation cycle; a sync fault must not reach the ledger; and a reconnection is healthy only when the silent interval has been backfilled and the statement closes, not when the token works again.",
      "tags": [
        "winstwaker",
        "reconciliatie",
        "webhooks",
        "volledigheid"
      ],
      "note": "Een groene webhook-status en een leeg foutenlogboek bewijzen niets: een gemiste levering laat geen gat achter, maar niets. Dit paper legt vast wanneer een periode volledig is, namelijk als de eigen telling en som gelijk zijn aan die van de bron.",
      "pages": 12,
      "words": 6095,
      "bytes": 271366,
      "size": "265 kB",
      "added": "2026-08-15",
      "related": [
        "2025-when-summation-and-rounding-fail-to-commute"
      ],
      "pdf": "/research/papers/2026-absence-of-errors-is-not-evidence-of-completeness.pdf",
      "txt": "/research/txt/2026-absence-of-errors-is-not-evidence-of-completeness.txt",
      "url": "/research/2026-absence-of-errors-is-not-evidence-of-completeness.html",
      "hasText": true,
      "relatedItems": [
        {
          "slug": "2025-when-summation-and-rounding-fail-to-commute",
          "title": "When Summation and Rounding Fail to Commute",
          "url": "/research/2025-when-summation-and-rounding-fail-to-commute.html",
          "year": 2025
        }
      ]
    },
    {
      "slug": "2025-when-summation-and-rounding-fail-to-commute",
      "title": "When Summation and Rounding Fail to Commute",
      "subtitle": "Nine elementary questions that a fiscal product cannot leave implicit",
      "year": 2025,
      "type": "paper",
      "typeLabel": "working paper",
      "authors": [
        "Kylian de Groot"
      ],
      "abstract": "The questions in this paper are elementary. They can be stated in one line each, and a reader who has divided integers will already suspect the answers. That is not a reason to leave them unwritten. Winstwaker is a product that must turn an integer-cent ledger into a whole-euro Dutch VAT return, and that must let software and language-model agents propose the same turn. Every wrong answer to these questions has a concrete product failure: two totals for one period, a year that is not the year, an amendment that is not the amendment, a \"check\" that invents tax. This paper therefore does one thing. It states nine questions. It answers each of them by arithmetic in Z. The answers are: rounding does not commute with addition; the filed payable total is not the rounding of the cent-level total; a position in cents can file as minus one euro; a filed euro cannot be inverted; a credit of 101 cents of VAT due files as minus two euros, not minus one; four filed quarters are not the filed year; rate times base is not booked tax; a mixed remainder vector files a different net from the rounding of its cent-level net; and the amendment of a filed period is the difference of two filings, not the filing of a cent-level increment.",
      "tags": [
        "winstwaker",
        "btw",
        "gehele deling",
        "afronding"
      ],
      "note": "Winstwaker houdt de boeken in centen, maar de Nederlandse btw-aangifte vraagt hele euro's. Dit paper schrijft uit wat er dan misgaat als je die stap als gewone eenheidsconversie behandelt.",
      "pages": 14,
      "words": 5974,
      "bytes": 281029,
      "size": "274 kB",
      "added": "2025-04-04",
      "related": [
        "2026-absence-of-errors-is-not-evidence-of-completeness"
      ],
      "pdf": "/research/papers/2025-when-summation-and-rounding-fail-to-commute.pdf",
      "txt": "/research/txt/2025-when-summation-and-rounding-fail-to-commute.txt",
      "url": "/research/2025-when-summation-and-rounding-fail-to-commute.html",
      "hasText": true,
      "relatedItems": [
        {
          "slug": "2026-absence-of-errors-is-not-evidence-of-completeness",
          "title": "Absence of Errors Is Not Evidence of Completeness",
          "url": "/research/2026-absence-of-errors-is-not-evidence-of-completeness.html",
          "year": 2026
        }
      ]
    }
  ]
}