lang-uk/perestoroha-ocr

Perestoroha OCR

Handwritten index cards containing a 20th-century scholarly transcription of the early 17th-century Ukrainian polemical text Perestoroha (Пересторога) by Iov Boretskyi (Lviv, 1605–1606). The cards preserve Old Ukrainian / Ruthenian orthography with archaic diacritics, historical letters (ѣ, ѳ, ѵ), and the source's distinctive line-by-line layout. Each record pairs a 300 DPI card image with line-aligned ground-truth text.

This dataset accompanies the paper "Digitizing Old Ukrainian Texts: A Prompt-Based OCR Pipeline and Evaluation Dataset" (Chaplynskyi & Dydyk-Meush, 2026) and the companion code repository at https://github.com/lang-uk/slavon_ocr.

Quick start

from datasets import load_dataset

ds = load_dataset("lang-uk/perestoroha-ocr")
print(ds)
# DatasetDict({train: 278, validation: 122, test: 30})

example = ds["test"][0]
example["image"]            # PIL.Image — 300 DPI JPEG, upright
example["transcription"]    # str — proofread text, line breaks preserved
example["source_reference"] # str — e.g. "Перест. 26."

Splits

Split	Cards	Provenance
train	278	Cards 153–460 — proofread later; transcribed with Claude Opus 4.7 (xhigh thinking) + the final prompt iteration
validation	122	The 122-card dev split used for prompt iteration (see paper §6). First-batch cards (Opus 4.6 + early prompt).
test	30	The 30-card held-out test split used for final evaluation (paper §5.3). First-batch cards (Opus 4.6 + early prompt).

The test/validation cards were drawn from the first ~152 proofread cards using a deterministic CER-stratified bucketing (seed=0). The train split is the remainder of the proofread corpus and was not used for any model selection in the paper — it's released as supplementary high-quality OCR training data.

Schema

Field	Type	Description
id	string	Card identifier, e.g. Auto-Color0002/001
image	Image	300 DPI JPEG, EXIF orientation already applied (cards are upright)
transcription	string	Proofread Old Ukrainian text. \r\n (CRLF) line breaks preserved for image-text alignment. The final line is the editorial source annotation (e.g. Львів, 1605-1606, Перест. 38) written by the 20th-century researcher who made the card; the source_city / source_date / source_reference fields are parsed equivalents. Strip the trailing source line if you need just the Perestoroha text.
card_num_primary	string | null	Primary card number on the index card
card_num_secondary	string | null	Secondary number where present
card_num_tertiary	string | null	Tertiary number where present
card_num_notes	string | null	Free-text proofreader notes on the numbering scheme
source_city	string | null	Manuscript provenance city (typically Львів)
source_date	string | null	Manuscript date (typically 1605-1606)
source_reference	string | null	Source-line reference (typically Перест. NN)
notes	string | null	Proofreader notes about textual uncertainty
reviewed_at	string	ISO-8601 UTC timestamp of proofreading

Orthographic conventions

The transcriptions preserve the source manuscript's orthography as faithfully as practical, except:

• Titlo abbreviations are silently expanded to full orthography. Nomina sacra and other commonly abbreviated words (Богъ, Христосъ, святый, патріархъ, etc.) appear in full form rather than as titlo-marked contractions.
• No combining diacritics are used. The single occurrence of a combining macron (card 441) is an isolated exception.
• Editorial brackets mark restored or interpolated text: ‹ › for editor-supplied passages.

Historical letters retained:

• ѣ (yat) — 899 occurrences
• ѳ (fita) — 9 occurrences (only in Greek-derived spellings: каѳолическоє, Тимоѳей, Маѳ., Коринѳу)
• ѵ (izhitsa) — 2 occurrences (only in еѵангелію)
• ү (U+04AF) — 28 occurrences, used distinctly from у to mark a specific handwritten glyph variant

Source material

The cards were produced by 20th-century researchers at the I. Krypiakevych Institute of Ukrainian Studies of the National Academy of Sciences of Ukraine. Each card excerpts a passage of the 1605–1606 Perestoroha manuscript and annotates it with provenance metadata. The cards are part of an extended lexicographic project on the language of early modern Ukrainian polemical literature.

The source text — Perestoroha itself — is in the public domain (composed 1605–1606). The transcriptions on the cards are 20th-century scholarly work; ground-truth proofreading (2026) is the editorial contribution of the paper authors.

License

Released under CC-BY-4.0. If you use this dataset, please cite the paper below.

Citation

@inproceedings{chaplynskyi-dydyk-meush-2026-perestoroha,
  title     = {Digitizing Old Ukrainian Texts: A Prompt-Based {OCR} Pipeline and Evaluation Dataset},
  author    = {Chaplynskyi, Dmytro and Dydyk-Meush, Hanna},
  year      = {2026},
  note      = {Companion repository: \url{https://github.com/lang-uk/slavon_ocr}}
}

Acknowledgements

We thank the I. Krypiakevych Institute of Ukrainian Studies for access to the source card collection.