# Changelog

All notable changes to the Universal Dependencies HuggingFace dataset loader will be documented in this file.

The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).

## [2.0.1] - 2026-01-14

### Added

- **Blocked Treebanks Support**
  - Added `blocked_treebanks.yaml` configuration for license-restricted treebanks
  - Metadata generation now includes "blocked" property for each treebank
  - Dataset card (README.md) automatically filters blocked treebanks from configs
  - See [tools/BLOCKED_TREEBANKS.md](tools/BLOCKED_TREEBANKS.md) for details

- **Documentation Improvements**
  - Added [RELEASE.md](RELEASE.md) - Framework version release guide
  - Updated [MIGRATION.md](MIGRATION.md) - Documents external ud-hf-parquet-tools library
  - Rewrote [tools/README.md](tools/README.md) - Concise quick reference for developers
  - Updated [ADDING_NEW_UD_VERSION.md](ADDING_NEW_UD_VERSION.md) - Comprehensive guide with current architecture
  - Added comprehensive Python patterns to `.gitignore`

### Changed

- **Script Renaming for Clarity**
  - `02_traverse_ud_repos.py` → `02_generate_metadata.py` (better reflects purpose)
  - `03_fill_universal_dependencies_tamplate.py` → `03_generate_README.py` (fixed typo, clarified scope)
  - Updated all documentation and workflows to reference new names

- **Tooling Simplification**
  - Removed generation of `universal_dependencies-{VER}` files (obsolete with Parquet-only architecture)
  - Removed `templates/universal_dependencies.tmpl` (no longer needed)
  - Moved tests to external `ud-hf-parquet-tools` library
  - `03_generate_README.py` now only generates README, not Python loader script

- **Metadata Generation**
  - `02_generate_metadata.py` now reads `blocked_treebanks.yaml` and adds blocked status to metadata
  - Enhanced logging for blocked treebanks

- **Template Updates**
  - `templates/README.tmpl` now filters blocked treebanks from configs section
  - Updated CONLLU_PARSING documentation link to point to ud-hf-parquet-tools repository

### Fixed

- **License Compliance**
  - Properly excludes treebanks with restrictive licenses (e.g., CC BY-NC-SA) that prohibit redistribution in derived formats
  - Currently excludes: pt_cintil (Portuguese-CINTIL)

### Removed

- **Obsolete Files**
  - Removed all `universal_dependencies-2.{7-17}` generated files (11 files)
  - Removed `templates/universal_dependencies.tmpl` template
  - Removed local `tests/` directory (functionality moved to ud-hf-parquet-tools)

### Documentation

All documentation now reflects the current architecture:
- No Python script loader (Parquet-only)
- External helper library (ud-hf-parquet-tools)
- Blocked treebanks handling
- Updated script names and workflows

## [2.0.0] - 2026-01-09

### Breaking Changes

- **Requires datasets>=4.0.0** for Parquet format support
  - Python dataset scripts are deprecated in datasets 4.0.0 (July 2025)
  - Parquet format is now the primary distribution method

- **Token sequences now correctly exclude MWT forms**
  - Previous versions incorrectly included Multi-Word Token (MWT) surface forms in token sequences
  - Token counts now match `num_words` from stats.xml, not `num_tokens`
  - Affects ~50+ treebanks with contractions (French, Italian, Portuguese, Spanish, Arabic, etc.)
  - **Example:** French "des" (MWT 18-19) → "de" + "les" (syntactic words 18, 19)
    - **v1.x (buggy):** tokens = [..., "des", "de", "les", ...]
    - **v2.0 (correct):** tokens = [..., "de", "les", ...], mwt = [{"id": "18-19", "form": "des", "misc": ""}]

### Added

- **Multi-Word Token (MWT) Support**
  - New `mwt` field in dataset schema containing structured MWT information
  - Schema: `[{"id": "1-2", "form": "surface_form", "misc": "metadata"}]`
  - Enables research on contractions, clitics, and word segmentation across languages
  - MWT statistics now collected from stats.xml (`num_fused` field)

- **Parquet Format Distribution**
  - All 339 treebanks available as Parquet files for efficient loading
  - 5-10x faster loading compared to on-the-fly CoNLL-U parsing
  - Reduced memory footprint and better compression
  - Compatible with HuggingFace datasets >=4.0.0

- **Separate Semantic Versioning**
  - Loader version (2.0.0) now tracked independently from UD data version (2.17)
  - Version in pyproject.toml reflects codebase changes
  - UD data version remains in dataset configuration
  - Enables clearer communication of breaking changes in tooling

- **Parquet Generation Pipeline**
  - New `tools/04_generate_parquet.py` script for CoNLL-U → Parquet conversion
  - Supports batch processing and validation
  - Test mode for quick iteration (`--test` flag)
  - Progress tracking and error reporting

### Fixed

- **Critical Bug: MWT lines incorrectly included in token sequences**
  - Fixed filtering in `_generate_examples()` to exclude MWT lines (tuple IDs) and empty nodes
  - Now uses `sent.filter(id=lambda x: type(x) is int)` to extract only syntactic words
  - Impact: Token counts were inflated by ~0.1-2% in affected treebanks
  - All token-level annotations (lemmas, UPOS, XPOS, features, heads, deprels) now correctly aligned

### Changed

- **Dataset schema extended** (non-breaking addition)
  - Added `mwt` field to all treebanks (empty list for treebanks without MWTs)

- **Dependencies updated**
  - Added `pyarrow>=14.0.0` for Parquet support
  - Added `datasets>=4.0.0` for compatibility
  - Added `conllu>=5.0.0` for reliable CoNLL-U parsing

- **Metadata collection enhanced**
  - `tools/02_traverse_ud_repos.py` now extracts `<fused>` counts from stats.xml
  - Enables validation of MWT extraction accuracy

## [1.0.0] - 2025-12-01 (Retroactive)

### Initial Release

- Python dataset loader using `GeneratorBasedBuilder`
- On-the-fly download and parsing of CoNLL-U files from GitHub
- Support for 339 treebanks across 186 languages
- UD data version: 2.15-2.17
- Compatible with HuggingFace datasets <4.0.0 using `trust_remote_code=True`

### Features

- Dynamic loading from Universal Dependencies GitHub repositories
- Automatic train/dev/test split detection
- CoNLL-U format parsing with conllu library
- Dataset features: tokens, lemmas, UPOS, XPOS, features, heads, dependency relations
- Metadata: language codes, families, licenses, genres

### Known Issues (Fixed in 2.0.0)

- MWT lines incorrectly included in token sequences
- No explicit MWT information available to users
- Requires `trust_remote_code=True` (security concern)
- Incompatible with datasets >=4.0.0

---

## Migration Guide

See [MIGRATION.md](MIGRATION.md) for detailed migration instructions from v1.x to v2.0.

## Version Numbering

- **Loader version** (e.g., 2.0.0): Reflects changes to the loading infrastructure and tooling
- **UD data version** (e.g., 2.17): Reflects the Universal Dependencies release version

Both versions are tracked separately to provide clarity on what changed.