lacing 0.0.3

Interval annotation system

lacing

A standoff, interval-keyed annotation system. Pythonic core: a MutableMapping[TimeInterval, list[Annotation]] facade with rational time, ELAN-style tier stereotypes, and Allen's interval algebra. Designed for time-based media (audio, video, speech, music) but generalizes to any 1-D interval domain.

Status: Phase 0–1. Core data model, in-memory + SQLite stores, five round-trip adapters (Praat TextGrid, WebVTT, W3C Web Annotation, .annot SQLite, ELAN EAF), inter-annotator agreement metrics, and a lacing CLI (convert, query, validate, list-formats). Server and frontend are on the roadmap (see misc/docs/Lacing Development Roadmap.md).

Install

pip install lacing                # core only
pip install 'lacing[textgrid]'    # + Praat TextGrid support (praatio)
pip install 'lacing[eaf]'         # + ELAN EAF support (pympi-ling)
pip install 'lacing[postgres]'    # + PostgresStore (psycopg + GiST + EXCLUDE)

30-second tour

from lacing.adapters import textgrid, webvtt, web_annotation  # registers each
from lacing.adapters import load, dump

# Load a Praat TextGrid → an in-memory store keyed by interval
store = load("speech.TextGrid", rate=1000)

# Query overlaps using Allen's relations
from lacing.time import RationalTime, TimeInterval
window = TimeInterval(RationalTime(500, 1000), RationalTime(1500, 1000))

for ann in store.intersects(window):
    print(ann.tier, ann.body["text"])

for ann in store.during(window):  # strictly inside the window
    ...

# Save out as WebVTT
dump(store, "speech.vtt", format="webvtt")

# Or as W3C Web Annotation JSON-LD
dump(store, "speech.jsonld", format="web_annotation")

What's in the core

lacing/
├── time.py          RationalTime + TimeInterval — rational, half-open, never float
├── model.py         Annotation envelope + Reference union + Provenance (PROV-O subset)
├── tier.py          Tier + 5 ELAN tier stereotypes + constraint validator
├── allen.py         13 Allen relations + intersects + relate + composition
├── store/
│   ├── base.py      IntervalAnnotationStore (MutableMapping facade)
│   ├── memory.py    MemoryStore over `intervaltree`
│   ├── sqlite.py    SqliteStore — persistent backend + .annot file format
│   └── postgres.py  PostgresStore — int8range + GiST + per-tier EXCLUDE
├── adapters/
│   ├── textgrid.py        Praat .TextGrid (interval + point tiers)
│   ├── webvtt.py          .vtt subtitles/captions
│   ├── web_annotation.py  W3C Web Annotation Data Model (JSON-LD)
│   ├── annot.py           .annot SQLite portable file format (lossless)
│   └── eaf.py             ELAN EAF (4 stereotypes verbatim)
├── cli.py           `lacing` CLI: convert, query, validate, list-formats
├── quality.py       Cohen's κ, Krippendorff's α, interval IoU, boundary IoU
├── schema.py        Body schema registry + JSON Schema export + migrations
└── bodies/          Built-in body schemas (word, named-entity, ...)

Design rules in one breath

1. Time is rational — RationalTime(value: int, rate: int). Wire format {v, r}. Never floats.
2. Standoff — annotations reference media by (asset_id, interval); source is immutable.
3. One envelope, typed body — Annotation.body: dict validated by body_schema_uri (semver).
4. Allen's algebra is the public predicate API — never write ad-hoc overlap checks.
5. ELAN tier stereotypes verbatim — NONE, TIME_SUBDIVISION, INCLUDED_IN, SYMBOLIC_SUBDIVISION, SYMBOLIC_ASSOCIATION.
6. PROV-O provenance inline on every annotation — was_generated_by, was_attributed_to, was_derived_from, generated_at_time.
7. MIT/BSD/Apache licenses only.

The full reasoning lives in misc/docs/ — four design docs covering annotation systems generally, backend architecture, frontend UI, and an OSS deep-dive of what to build on. The synthesized plan is in misc/docs/Lacing Development Roadmap.md.

Concrete recipes

Build annotations programmatically

from uuid import uuid4
from lacing import (
    Annotation, MediaRef, MemoryStore, Provenance,
    RationalTime, TimeInterval, Tier,
)

store = MemoryStore()
store.add_tier(Tier("words"))

store.add(Annotation(
    id=uuid4(),
    tier="words",
    reference=MediaRef(
        asset_id="blake3:abc123",
        interval=TimeInterval.from_seconds("0.0", "0.5", rate=1000),
    ),
    body={"text": "hello"},
    body_schema_uri="annot://schema/word/v1",
    provenance=Provenance(
        was_generated_by="user:thor",
        was_attributed_to="thor",
        generated_at_time=RationalTime.zero(1000),
    ),
))

Query with Allen's relations

from lacing.allen import AllenRelation
from lacing.time import RationalTime, TimeInterval

w = TimeInterval(RationalTime(0, 1000), RationalTime(500, 1000))

list(store.intersects(w))                       # any overlap
list(store.during(w))                           # strictly inside w
list(store.contains(w))                         # strictly contains w
list(store.relate(w, [AllenRelation.MEETS]))   # ends at w.start

Persist annotations

from lacing.store import SqliteStore

# Open or create a .annot file (SQLite under the hood)
store = SqliteStore("project.annot")
store.add_tier(...)
store.add(...)            # writes go straight to disk
store.set_meta("project", "demo")

# Same MutableMapping + Allen-relation interface as MemoryStore
for ann in store.intersects(window):
    ...
store.close()

The .annot file is the recommended portable handoff format — single-file SQLite, Git-trackable, lossless round-trip with MemoryStore.

For multi-user / production scale, the same facade is available over PostgreSQL:

from lacing.store import PostgresStore
from lacing.tier import Tier

store = PostgresStore("postgresql://localhost/myproject", rate=1000)

# Per-tier non-overlap is enforced declaratively by the database — try to
# add an overlapping annotation in this tier and Postgres rejects the insert.
store.add_tier(Tier("speakers"), enforce_no_overlap=True)

The Postgres backend uses int8range + GiST (sub-millisecond overlap queries at million-row scale) and exposes the same Allen-relation methods. Times are normalized to a project-wide rate stored in meta.

CLI

After pip install -e . the lacing command is on your PATH:

lacing list-formats                                          # show registered adapters
lacing convert speech.TextGrid speech.annot                  # convert between formats
lacing query speech.annot --start 1.0 --end 5.0 --rate 1000  # JSON-lines
lacing validate speech.annot                                 # parse + summary

Body schemas, validation, migrations

Every annotation has a body: dict validated against the schema named by its body_schema_uri (e.g., annot://schema/named-entity/v2). Register your own with a Pydantic v2 model:

from pydantic import BaseModel, Field
from lacing.schema import register_body_schema, register_migration, validate, migrate

class WordBodyV1(BaseModel):
    model_config = {"frozen": True, "extra": "forbid"}
    text: str = Field(...)
    speaker: str | None = None

register_body_schema("annot://schema/word/v1", WordBodyV1)

# Validate at runtime:
validate({"text": "hello"}, "annot://schema/word/v1")

# Register a forward migration v1 -> v2:
@register_migration(schema_name="word", from_version=1, to_version=2)
def _v1_to_v2(body: dict) -> dict:
    return {**body, "lemma": None}

# Migrate stored data:
migrated = migrate({"text": "ran"},
                   from_uri="annot://schema/word/v1",
                   to_uri="annot://schema/word/v2")

Export every registered schema to JSON Schema (the upstream for downstream Zod codegen):

from lacing.schema import export_json_schemas
export_json_schemas("./schema/")  # writes <name>/v<N>.json + index.json

Built-in body schemas live under lacing/bodies/ (word, named-entity). They register themselves on import.

Inter-annotator agreement

from lacing.quality import cohen_kappa, krippendorff_alpha, boundary_iou

# Two annotators on a categorical task
kappa = cohen_kappa(["A", "B", "A", "B"], ["A", "A", "A", "B"])

# Three annotators with missing data
alpha = krippendorff_alpha([
    ["A", "B", None, "C"],
    ["A", "B", "B",  "C"],
    ["A", "A", "B",  "C"],
])

# Compare two segmentations
score = boundary_iou(
    [a.interval for a in store_a.by_tier("speakers")],
    [a.interval for a in store_b.by_tier("speakers")],
)

License

MIT.