# 11. Corrections

A correction, `scienting-correction/1`, is an operation on an established document, with its evidence and its author.
Corrections are added and never edited, so a document's history is its original reading plus its corrections.
Each has an `index`, counted from 1 in the order corrections are applied, and the document's revision is the index of the last.

## 11.1 Operations

| `op` | Fields | Does | IDs |
| --- | --- | --- | --- |
| `replace` | `target`, `find`, `replace`, optional `run` | Replaces the one occurrence of `find` among the target's editable strings with `replace`, a string or, inside a text run, a list of runs. | Unchanged. |
| `insert` | `parent`, `place_after` (a sibling, or null for first), `node` | Adds a subtree: kinds, labels, attributes and content, with each equation run naming its child as `{"kind": "equation", "child": i}`. | New IDs, minted ([4.2](04-identity.md#42-minting-node-ids)). |
| `insert` | `target`, `run`, `offset`, `text` | Inserts text into one run of the target, at a code-point offset in that run's editable string. | Unchanged. |
| `delete` | `target` | Removes an artifact and its subtree, such as a running head read as text. | All retired, without successors. |
| `split` | `target`, `offset` | Splits a sentence at an offset in its plain projection, which falls between runs or inside a text run; whitespace at the split is removed from both parts, and each equation child goes with its run. | The first part keeps the ID; the second gets a new one. |
| `merge` | `target`, `with`, optional `joiner` | Joins a node with its next sibling of the same kind: the runs of two run-bearing nodes, with the joiner (default one space) between, or the children of two `paragraph`, `list`, `item`, `quote`, `caption`, `figure-note` or `table-note` nodes. | `with` is retired, with the target as successor. |
| `move` | `target`, `parent`, `place_after` | Changes reading order or containment. | Unchanged. |
| `reclassify` | `target`, `kind` | Changes a node's kind, such as a paragraph that is really a caption, to a kind with the same content shape. | Unchanged. |
| `relabel` | `target`, `label` | Changes a printed label. | Unchanged. |
| `set` | `target`, `attr`, `value` | Sets one structural attribute: a section's `level`, a table's `columns`, a cell's `column`, `rowspan`, `colspan` or `role`, a row's `header_path`, a list's `ordered`, an item's `marker` or a theorem's `variant`. | Unchanged. |

A leaf's editable strings are the `text` of its `text`, `link`, `cite`, `xref` and `fnmark` runs and the `source` of its `math` runs, each searched on its own; an equation's `source`; a verbatim node's `text`.
`set` exists because readings drop spans, roles and header paths; see the [rationale](../docs/rationale.md#corrections).
Runs are made canonical after every operation, and the result MUST satisfy every rule of [3](03-nodes.md).

## 11.2 Every correction records

| Property | Holds |
| --- | --- |
| `evidence` | At least one item: `crop`, `witness` or `source-file` by SHA-256, or `person`. |
| `author` | `{key}` for a person in the roster, or `{model, run}` for a model's session. |
| `reason`, `at` | Why, and when. |

A proposal, such as one a tool makes, carries these and `status: "proposed"`, and no applied fields.

## 11.3 Applied fields

When a correction is applied, its record gains:

| Property | Holds |
| --- | --- |
| `index`, `id` | Its position, and its record ID. |
| `before`, `after` | The target's `node_hash` before and after, or null; for an inserted subtree, `target` is its root. |
| `path` | The target's ancestors when it was applied, root first; for an insert, the new subtree's. |
| `to_path` | For a move, the new ancestors. |
| `touched` | The leaves whose content the correction changed, sorted: the target of a `replace`, text `insert`, `relabel` or `set` on a leaf; the new leaves of a node `insert`; the deleted leaves of a `delete`; both parts of a `split`; both nodes of a run `merge`, or the moved-in leaves of a container `merge`; the moved leaves of a `move`; the leaves of a reclassified node. |
| `created`, `retired` | IDs minted or retired. |
| `from` | The label, kind or attribute value before a `relabel`, `reclassify` or `set`. |

Retirements are also entered in `ids.jsonl` with the correction's index as `rev`.
Drift ([6.6](06-anchors.md#66-drift)) is computed from `path`, `to_path` and `touched` alone, so it needs no replay.

## 11.4 The gate

A correction is refused, naming the rule ([22](22-conformance.md)), when:

1. it does not match the correction schema, `schemas/correction.schema.json`;
2. a target, parent or sibling is not live, or the root would be deleted, moved, merged or reclassified;
3. `find` is empty or does not occur exactly once;
4. an `insert` has no crop evidence, or names a run or offset its target does not have;
5. a digit changes without crop evidence: in a `replace` whose `find` and replacement have different digits, a `delete` of leaves that hold digits, or a `relabel` whose labels have different digits;
6. any leaf outside `touched` has different digits afterwards;
7. a `split` falls outside the sentence, inside a run other than text, or leaves a part empty;
8. a `merge` joins nodes that differ in kind, are not mergeable, or are not adjacent siblings;
9. a `move` would put a node inside itself;
10. a `reclassify` changes the content shape, or a `relabel` or `set` targets a kind that does not take it; or
11. the result breaks a rule of [3](03-nodes.md).

The gate needs only the document's current state, so a tool can run it on a proposal before applying anything, and get back the record the correction would append or the rule it breaks.
`tools/validate.py --correction` does this against a package.

Digits are characters of General Category Nd in the plain projection.
A package's corrections are also checked as a whole: indexes run from 1 without gaps, each `id` derives from its record, `rev` equals their number, every retired ID is in `ids.jsonl`, and the last correction of each leaf ends at its current `node_hash`.
`corrections.jsonl` in the vectors applies each operation, and each refusal, to a small document.