# Store shared product facts separately from differing variant facts

Keep the shared note once while showing the correct cable length for each lamp variant.

## Find the facts that really stay the same

The fictional lamp product has a supplied note ID NOTE-W shared by both variants. The black cable is 1 metre and the white cable is 2 metres. The note ID is opaque: it contains no warranty recommendation. This model stores the shared note at product level and cable metres at variant level. It reports a common cable value only when every variant has the same known value.

Filled lamp specification sheet

| Record | Shared note | Cable metres | Field owner |
| --- | --- | --- | --- |
| Lamp | NOTE-W | No common value | Product |
| black | NOTE-W | 1 | Variant |
| white | NOTE-W | 2 | Variant |

## Display each offer without inventing inheritance

A product-level 1-metre cable value would misdescribe white. Keeping 1 and 2 on the variants represents both offers while retaining NOTE-W once in the source. Choosing a variant still needs the separate stock identity contract; a cable field does not select a SKU.

1. List supplied product facts
2. Compare every offered variant
3. Keep differing fields on variants
4. Render each offer’s known fields

A missing variant value does not inherit the other variant’s value.

If white also has an evidenced 1-metre cable, what is the common value?

1 metre. Both known variant values match. That possible common value does not change variant IDs or stock balances.

## Prepare a field-scope brief

The complete material compares different lengths, equal lengths and unknown white length. Use it to specify product/variant presentation fields before a catalogue build; keep operational SKU records separately owned.

Cable values are positive whole metres up to 1,000 or null under this narrow example. Null white length gives no common value and an unknown variant, rather than a guessed 1-metre result. No measurement conversion, legal note interpretation or supplier claim is performed.

Use this product-data brief when discussing catalogue fields, then inspect definition review before applying stricter validations.

## Complete local records and trace

```json
{
  "issuer": "Astera Technology",
  "resource": "ops-product-field-owner-scope",
  "locale": "en",
  "contract": "The fictional lamp product has a supplied note ID NOTE-W shared by both variants. The black cable is 1 metre and the white cable is 2 metres. The note ID is opaque: it contains no warranty recommendation. This model stores the shared note at product level and cable metres at variant level. It reports a common cable value only when every variant has the same known value.",
  "input": {
    "product": "Lamp",
    "sharedNote": "NOTE-W",
    "variants": [
      {
        "id": "black",
        "cableMetres": 1
      },
      {
        "id": "white",
        "cableMetres": 2
      }
    ]
  },
  "output": {
    "ok": true,
    "state": "complete",
    "result": {
      "product": "Lamp",
      "sharedNote": "NOTE-W",
      "commonCableMetres": null,
      "variants": [
        {
          "id": "black",
          "cableMetres": 1,
          "sharedNote": "NOTE-W",
          "decision": "known"
        },
        {
          "id": "white",
          "cableMetres": 2,
          "sharedNote": "NOTE-W",
          "decision": "known"
        }
      ]
    },
    "trace": [
      {
        "id": "black",
        "cableMetres": 1,
        "sharedNote": "NOTE-W",
        "decision": "known"
      },
      {
        "id": "white",
        "cableMetres": 2,
        "sharedNote": "NOTE-W",
        "decision": "known"
      }
    ]
  },
  "verificationCases": [
    {
      "name": "baseline",
      "input": {
        "product": "Lamp",
        "sharedNote": "NOTE-W",
        "variants": [
          {
            "id": "black",
            "cableMetres": 1
          },
          {
            "id": "white",
            "cableMetres": 2
          }
        ]
      },
      "expected": {
        "ok": true,
        "state": "complete",
        "result": {
          "product": "Lamp",
          "sharedNote": "NOTE-W",
          "commonCableMetres": null,
          "variants": [
            {
              "id": "black",
              "cableMetres": 1,
              "sharedNote": "NOTE-W",
              "decision": "known"
            },
            {
              "id": "white",
              "cableMetres": 2,
              "sharedNote": "NOTE-W",
              "decision": "known"
            }
          ]
        }
      }
    },
    {
      "name": "material-edit",
      "input": {
        "product": "Lamp",
        "sharedNote": "NOTE-W",
        "variants": [
          {
            "id": "black",
            "cableMetres": 1
          },
          {
            "id": "white",
            "cableMetres": 1
          }
        ]
      },
      "expected": {
        "ok": true,
        "state": "complete",
        "result": {
          "product": "Lamp",
          "sharedNote": "NOTE-W",
          "commonCableMetres": 1,
          "variants": [
            {
              "id": "black",
              "cableMetres": 1,
              "sharedNote": "NOTE-W",
              "decision": "known"
            },
            {
              "id": "white",
              "cableMetres": 1,
              "sharedNote": "NOTE-W",
              "decision": "known"
            }
          ]
        }
      }
    },
    {
      "name": "fresh-boundary",
      "input": {
        "product": "Lamp",
        "sharedNote": "NOTE-W",
        "variants": [
          {
            "id": "black",
            "cableMetres": 1
          },
          {
            "id": "white",
            "cableMetres": null
          }
        ]
      },
      "expected": {
        "ok": true,
        "state": "unknown",
        "result": {
          "product": "Lamp",
          "sharedNote": "NOTE-W",
          "commonCableMetres": null,
          "variants": [
            {
              "id": "black",
              "cableMetres": 1,
              "sharedNote": "NOTE-W",
              "decision": "known"
            },
            {
              "id": "white",
              "cableMetres": null,
              "sharedNote": "NOTE-W",
              "decision": "unknown"
            }
          ]
        }
      }
    }
  ],
  "meaningOfNull": "Unknown or no established value for the field; inspect its specific trace.",
  "businessSideEffects": false
}
```