---
language:
- bo
license: other
task_categories:
- token-classification
pretty_name: Tibetan Annotation Layer Detection
tags:
- tibetan
- openpecha
- tsadra
- ner
- quotation
- span-detection
- buddhist-studies
size_categories:
- n<1K
---

# Tibetan Annotation Layer Detection

266 annotated Classical Tibetan books with seven annotation layers — Quotation,
Sabche, Tsawa, Yigchung, Chapter, Author, BookTitle — stored as character-offset
spans over a flat base text. Each row is one book: `book_id`, `text`, `spans`
(`{start, end, label}`), and `in_scope_layers`.

Book-level split: **217 train / 25 validation / 24 test**. A book is never split
across partitions.

This revision (`v1.1`) is a span-level clean of `v1.0`. Texts, book membership,
split assignment, and split order are unchanged.

## What changed in v1.1

Every span with `start == end` was dropped, on all seven layers. No other spans
were removed. Impossible geometries (`start > end`, negative offsets, offsets
beyond the book text) were scanned and **none were found**.

Character mass uses inclusive length `end - start + 1` (see caveat below).

| Layer | Spans before | Spans after | Removed | Char mass before | Char mass after |
|---|---:|---:|---:|---:|---:|
| Quotation | 24,730 | 24,722 | 8 | 3,415,105 | 3,415,097 |
| Sabche | 18,847 | 18,845 | 2 | 1,608,291 | 1,608,289 |
| Tsawa | 6,845 | 6,811 | 34 | 1,285,298 | 1,285,264 |
| Yigchung | 9,025 | 8,804 | 221 | 841,535 | 841,314 |
| Chapter | 1,637 | 1,637 | 0 | 94,724 | 94,724 |
| Author | 311 | 311 | 0 | 12,160 | 12,160 |
| BookTitle | 266 | 266 | 0 | 21,938 | 21,938 |
| **Total** | **61,661** | **61,396** | **265** | **7,279,051** | **7,278,786** |

All 265 removals were `start == end`. 43 books lost at least one span:

| Book | Spans removed |
|---|---:|
| P000036 | 58 |
| P000140 | 33 |
| P000236 | 21 |
| P000275 | 20 |
| P000087 | 16 |
| P000123 | 14 |
| P000153 | 14 |
| P000195 | 8 |
| P000138 | 6 |
| P000073 | 5 |
| P000132 | 5 |
| P000174 | 4 |
| P000030 | 4 |
| P000034 | 3 |
| P000037 | 3 |
| P000054 | 3 |
| P000089 | 3 |
| P000119 | 3 |
| P000130 | 3 |
| P000152 | 3 |
| P000159 | 3 |
| P000010 | 3 |
| P000011 | 3 |
| P000171 | 3 |
| P000218 | 3 |
| P000055 | 2 |
| P000199 | 2 |
| P000230 | 2 |
| P000021 | 1 |
| P000028 | 1 |
| P000050 | 1 |
| P000051 | 1 |
| P000096 | 1 |
| P000126 | 1 |
| P000156 | 1 |
| P000175 | 1 |
| P000203 | 1 |
| P000207 | 1 |
| P000216 | 1 |
| P000224 | 1 |
| P000258 | 1 |
| P000151 | 1 |
| P000246 | 1 |

`v1.0` remains reachable as the `v1.0` tag (commit `aaa17607`).

## Why

`start == end` spans are zero-length or one-character stray marks, not real
annotations. The previous validator only checked geometric coherence (negative,
inverted, out of bounds), so these passed silently.

## Flagged books (zero spans for an in-scope layer)

These books are **retained**. Their in-scope layer with no remaining spans is
unresolved — they are not dropped from the split.

- **P000218** (test): 847,725 characters; had 3 Quotation spans, all `start == end`.
  After this clean it has **no Quotation annotation at all**, while still marked
  in-scope for Quotation.
- **P000126** (train): already had **zero** Quotation spans while marked in-scope.
  Unchanged by this clean (one non-Quotation `start == end` span was dropped).

No other in-scope layer on any book went to zero spans as a result of this clean.

## Known remaining issues (not fixed here)

- Some books have very low annotation density relative to their length.
- Some books have large positional gaps with no annotation.
- Damage has only been systematically examined for **Quotation**. The other six
  layers were cleaned of `start == end` here but have not been inspected for
  density or gaps.
- No minimum-length rule, density filter, or gap detection was applied.

The offset convention (inclusive vs half-open) has not been independently verified.

## License

Packaging, split, and this clean are released under CC0 1.0. Underlying texts and
original annotations come from OpenPecha / Tsadra; per-book source licenses vary.