Claim and slot keys

Umwelt derives stable lowercase hexadecimal SHA-256 keys from UTF-8 encoded canonical JSON.

claimKey

The claimKey input object contains exactly these fields:

{
  "subject": "...",
  "predicate": "...",
  "object": {},
  "qualifiers": {},
  "about": null
}

slotKey

The slotKey input object contains exactly subject and predicate:

{"subject":"...","predicate":"..."}

Canonical JSON is produced recursively with these rules:

• Object keys are sorted by Unicode code point order.
• No insignificant whitespace is emitted.
• Strings use the implementation’s exact JSON escaping: quotation mark, reverse solidus, backspace, form feed, newline, carriage return, and tab use their short escapes; other control characters from U+0000 through U+001F use lowercase four-digit \u escapes; all other Unicode scalar values are emitted unchanged.
• Numbers use the serde_json representation. In particular, 1 and 1.0 are different values and produce different canonical JSON.
• Unicode is not normalized.

The SHA-256 digest is calculated over the canonical JSON UTF-8 bytes and encoded as lowercase hexadecimal.

Fixed test vector

Input claim:

{"subject":"player","predicate":"gave-gift","object":{"kind":"entity","id":"mira"},"qualifiers":{"item":"lantern"},"polarity":true,"about":null}

{"about":null,"object":{"id":"mira","kind":"entity"},"predicate":"gave-gift","qualifiers":{"item":"lantern"},"subject":"player"}

a0a8d5482c1eb719682e2cf8ef931adb41673a7d6ce1c509a625e93cfa1ed391

On the wire and in every public API, claimKey and slotKey are the 64-character lowercase hex strings defined above. The SQLite store keeps only the first 16 bytes of each digest (128 bits, a BLOB) in its record table and indexes. Two different claims share a stored key only by a 128-bit SHA-256 prefix collision, the same odds as two random UUIDs being equal. The conversion happens only inside umwelt-sqlite. A string that is not 64 hex characters cannot match any stored key, so a query with such a key returns no rows rather than an error.