Improve dataset card: document schema, measured stats and limitations

README.md

@@ -22,3 +22,87 @@ configs:
   - split: test
     path: data/test-*
 ---
+
+# Script normalization CKB — noisy → standard Sorani (script_normalization_ckb)
+
+Nearly 6M sentence pairs: the `text` column holds Central Kurdish written with
+non-standard or distorted characters, `summary` holds the same sentence in standard
+Sorani orthography. Use it for text normalisation, spell correction, or to learn the
+character-level mapping rules.
+
+## At a glance
+
+| | |
+|---|---|
+| Rows | 5,997,025 — `train` 5,330,689 / `test` 666,336 |
+| Columns | `text` (noisy input), `summary` (normalised target) |
+| Parquet on disk | 904.5 MB (1.57 GB uncompressed) |
+| Row groups | 667 in the test shard, ~1,000 rows each |
+| Language | Central Kurdish / Sorani (ckb) |
+
+> **Naming note:** despite the column name, `summary` is **not** a summary — it is
+> the normalised rewrite of `text`. Both sides carry the same content.
+
+## How the two sides differ
+
+Measured on 1,000 rows of the `test` split:
+
+| | |
+|---|---|
+| Rows where `text` == `summary` | 20 (2%) |
+| Mean character-level edit distance | 21.5 |
+| Max edit distance | 85 |
+| Mean length `text` / `summary` | 69.3 / 67.3 chars |
+
+Which characters get fixed (rows affected out of 1,000):
+
+| Change | Rows |
+|---|---|
+| `ي` (U+064A Arabic yeh) → `ی` (U+06CC Farsi yeh) | 682 |
+| `ة` (U+0629 teh marbuta) → `ە` (U+06D5) | 384 |
+| `ه` (U+0647) → `ە` (U+06D5) | 397 |
+| `ث` (U+062B) → `س` (U+0633) | 114 |
+| `ذ` (U+0630) → `ز` (U+0632) | 68 |
+
+Example pair:
+
+```
+text    : يابان بؤ خؤي بش ئه و قه يرانه  طه نگوجه له مه ي ئابووري هه ره فراواني ...
+summary : یابان بۆ خۆی پێش ئەو قەیڕانە تەنگوچەلەمەی ئابووری هەرەفراوانی ...
+```
+
+Some rows are far noisier than character substitution:
+
+```
+text    : اهي اهگهر پئشمهرگه نهبايه حكمهطي بهعث عثهي پاقلاه ...
+summary : ئەی ئەگەر پێشمەرگە نەبووایە حکومەتی بەعس عوسەی پاقلاوەو ...
+```
+
+## Usage
+
+```python
+from datasets import load_dataset
+
+ds = load_dataset("razhan/script_normalization_ckb", split="test")
+print(ds[0]["text"])      # noisy
+print(ds[0]["summary"])   # standard
+
+# fine-tune any encoder-decoder for normalisation, or mine substitution rules:
+pairs = ds.select(range(200_000))
+```
+
+## Known limitations
+
+- The corpus is synthetic in construction: noise was introduced into clean text, so
+  the error distribution reflects the generator, not real user typos.
+- `summary` is the target and the column name is misleading (left in place for
+  backwards compatibility).
+- Only character/orthography-level repair is targeted; it does not correct grammar
+  or word choice, and heavily distorted rows can still normalise to a different
+  token sequence.
+- Rows are single sentences — no document context.
+
+## Related
+
+- `razhan/riste` — line-by-line Sorani sentences (a likely source pool).
+- `razhan/kteb`, `razhan/kteb-dataset` — book text in mixed orthography.