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Introduction

What is Layers?​

Layers is a set of ATProto Lexicon v1 schemas for representing, sharing, and interlinking linguistic annotation data in a decentralized network. It defines a composable interchange format for annotations across text, audio, video, and image modalities.

Layers subsumes 15+ major annotation data models—including CoNLL, CoNLL-U, brat, ELAN, TEI, WebVTT, VTT, Universal Dependencies, AMT, SRL, ARK, and others—while maintaining a theory-neutral, modular architecture. All annotation data lives in user-controlled Personal Data Servers (PDSes); Layers provides the schema and protocols for interoperability.

Why Layers?​

Linguistic annotation data is fragmented across incompatible formats, stored in centralized repositories, and lacks a common interchange layer:

  • Fragmentation: Each annotation task (part-of-speech tagging, dependency parsing, discourse analysis, etc.) has its own format—CoNLL, brat, ELAN, TEI, WebVTT—with no common schema for translation or composition.
  • Centralization: Datasets live in centralized repositories (Linguistic Data Consortium, GitHub, institutional servers) or isolated research databases. Users have no control over data access, licensing, or portability.
  • Lock-in: Annotations created in one tool cannot be easily imported into another. Interoperability requires custom conversion scripts that fail on edge cases.
  • Isolation: There is no standard way to link annotations to publications, relate annotations across records, or discover related work.

Layers solves this by:

  1. Defining shared primitives that all annotation types compose from (anchors, constraints, agents, metadata).
  2. Staying theory-neutral by representing all linguistic labels, categories, and formalisms as data values, not schema.
  3. Using ATProto for decentralization: all user data lives in their PDSes; annotations are ATProto records that users publish and control.
  4. Providing tight integration with publication metadata, knowledge bases (Wikidata, FrameNet, SRL databases), and existing tools (via W3C Web Annotation selectors).
  5. Supporting composition across modalities and annotation types through recursive cross-referencing. See the Multimodal Annotation guide for examples.

Status​

Layers is in v0.1.0 draft status, in active development and accepting comments and discussion. File issues or participate on GitHub: https://github.com/layers-pub/layers

Architecture Overview​

Layers is organized around a pipeline of annotation layers, each building on primitives from the layer before:

Expression (any linguistic unit: document, paragraph, sentence, word, morpheme)
       ↓
Segmentation (tokenization, chunking, segmentation bounds)
       ↓
Annotation (linguistic labels: POS, NER, semantic roles, etc.)

Expressions are recursive: a document contains paragraphs, which contain sentences, which contain words, which contain morphemes. Each Expression can reference its parent via parentRef, and Segmentation records define the ordered decomposition of a parent Expression into child Expressions.

Parallel tracks integrate this pipeline with external systems:

  • Ontology: authority records for label definitions, linguistic categories, frameworks.
  • Corpus: corpus metadata, membership, and statistics.
  • Resource: lexical entries, stimulus templates, and fillings.
  • Judgment: human and model judgments, confidence scores, disagreement metadata.
  • Alignment: cross-record linking, token sequence correspondence, equivalence.

Integration layers connect Layers to the ATProto ecosystem:

  • Graph: generic typed property graph for knowledge representation and cross-referencing.
  • Eprint: scholarly metadata, publication links, and data provenance.
  • Media: rich media attachments (audio, video, image references).
  • Persona: persona/agent metadata for attribution and tool tracking.

License​

Copyright © 2026 Aaron Steven White. Layers is licensed under CC-BY-SA-4.0.

Next Steps​

  • Read Foundations for design principles, primitives, and the flexible enum pattern.
  • See Lexicon Overview for the full list of schemas.
  • Explore the Guides for in-depth coverage of temporal, spatial, multimodal, and knowledge grounding topics.