HED schemas reference¶

This page provides detailed information about each available HED schema, including links to different formats, versions, and documentation.

Standard schema¶

The HED standard schema contains the basic vocabulary for annotating experiments across all domains.

Overview¶

Property	Value
Current Version	8.4.0
Prerelease Version	8.5.0
HedId Range	10000-39999
DOI	10.5281/zenodo.7876037
Release Date	June 1, 2024

Description¶

The HED standard schema provides fundamental terms for describing:

Events: Sensory presentations, experimental events, data features
Agents: Humans, animals, avatars performing actions
Actions: Movements, communications, cognitive processes
Items: Objects, geometric entities, biological items, language items
Properties: Characteristics describing agents, actions, and items
Relations: Spatial and logical relationships

Access Links¶

Format	Current Release (8.4.0)	Prerelease (8.5.0)
XML	Raw \| View	Raw \| View
MEDIAWIKI	Raw \| View	Raw \| View
JSON	Raw	Raw
TSV	Directory	Directory

Latest version (stable link): HEDLatest.xml

Documentation¶

References¶

Makeig, S. and K. Robbins (2024).
Events in context—The HED framework for the study of brain, experience and behavior.
Front. Neuroinform. Vol. 18. https://doi.org/10.3389/fninf.2024.1292667

Robbins, K., Truong, D., Jones, A., Callanan, I., & Makeig, S. (2021).
Building FAIR functionality: Annotating event-related imaging data using Hierarchical Event Descriptors (HED).
Neuroinformatics. https://doi.org/10.1007/s12021-021-09537-4

SCORE library schema¶

HED-SCORE implements the Standardized Computer-based Organized Reporting of EEG (SCORE) standard for clinical neurological annotation.

Overview¶

Property	Value
Current Version	2.1.0
Prerelease Version	2.2.0
HedId Range	40000-59999
DOI	10.5281/zenodo.7897596
Partnered With	Standard 8.3.0

Description¶

The SCORE library allows neurologists, neurophysiologists, and brain researchers to annotate electrophysiology recordings using terms from an internationally accepted set of defined terms compatible with the HED framework. The vocabulary covers:

Finding: EEG phenomena and patterns observed in recordings
Sleep-related: Sleep stages and sleep-specific phenomena
Modulators: Factors affecting EEG patterns (eye state, vigilance, medication)
Background-activity: Characteristics of ongoing EEG
Episode: Specific event types (seizures, epileptic episodes)

Access Links¶

Format	Current Release (2.1.0)	Prerelease (2.2.0)
XML	Raw \| View	Raw \| View
MEDIAWIKI	Raw \| View	Raw \| View
JSON	Raw	Raw
TSV	Directory	Directory

Latest version (stable link): HED_score_Latest.xml

Documentation¶

References¶

Hermes, D., Pal Attia, T., Beniczky, S. et al.
Hierarchical Event Descriptor library schema for EEG data annotation.
Sci Data 12, 1448 (2025). https://doi.org/10.1038/s41597-025-05791-2

Beniczky, S, et al. (2013). Standardized computer based organized reporting of EEG: SCORE.
Epilepsia 54.6 (2013).

Beniczky, S., et al. (2017). Standardized computer based organized reporting of EEG: SCORE second version.
Clinical Neurophysiology 128.11 (2017).

LANG library schema¶

The HED Language library schema (HED LANG) contains vocabulary for annotating language experiments in cognitive science.

Overview¶

Property	Value
Current Version	1.1.0
Prerelease Version	1.2.0
HedId Range	60000-79999
DOI	10.5281/zenodo.13987483
Partnered With	Standard 8.3.0

Description¶

HED LANG allows for detailed annotation of language stimuli at multiple levels through orthogonal definition of:

Language-item: Full sentences, words, morphemes, phonemes
Language-item-property: Linguistic characteristics applicable across languages
- Morphosyntactic properties (word class, case, tense, etc.)
- Semantic properties (concreteness, animacy, etc.)
- Orthographic properties (capitalization, script)
- Phonological properties (stress, syllable structure)

The schema supports both carefully controlled experiments addressing specific psycholinguistic questions and complex naturalistic paradigms.

Access Links¶

Format	Current Release (1.1.0)	Prerelease (1.2.0)
XML	Raw \| View	Raw \| View
MEDIAWIKI	Raw \| View	Raw \| View
JSON	Raw	Raw
TSV	Directory	Directory

Latest version (stable link): HED_lang_Latest.xml

Documentation¶

Example datasets¶

Annotated datasets using HED LANG are available:

References¶

Denissen, M., Pöll, B., Robbins, K., Makeig, S. & Hutzler, F.
HED LANG – A Hierarchical Event Descriptors library extension for annotation of language cognition experiments.
Sci Data 11, 1428 (2024). https://doi.org/10.1038/s41597-024-04282-0

SLAM library schema¶

The HED SLAM library schema provides vocabulary for Sensor Location and Motion annotation.

Overview¶

Property	Value
Current Version	- (prerelease only)
Prerelease Version	1.0.0
HedId Range	80000-99999
DOI	Not yet assigned
Partnered With	Standard 8.3.0

Description¶

HED SLAM is currently in prerelease development. This library will provide vocabulary for describing:

Sensor locations and positioning
Motion tracking and recording
Spatial relationships
Movement characteristics

Access Links¶

Format	Prerelease (1.0.0)
XML	Raw \| View
MEDIAWIKI	Raw \| View
JSON	Raw

Documentation¶

README

MOUSE library schema¶

The HED MOUSE library schema provides vocabulary for mouse/rodent experiment annotation.

Overview¶

Property	Value
Current Version	- (prerelease only)
Prerelease Version	1.0.0
HedId Range	100000-119999
DOI	Not yet assigned
Partnered With	Standard 8.3.0

Description¶

HED MOUSE is currently in prerelease development. This library will provide vocabulary specific to mouse and rodent experiments, including:

Rodent-specific behaviors
Experimental paradigms for animal studies
Sensory stimuli relevant to rodent research
Recording techniques specific to animal models

Access Links¶

Format	Prerelease (1.0.0)
XML	Raw \| View
MEDIAWIKI	Raw \| View
JSON	Raw

Documentation¶

README

TESTLIB library schema¶

The TESTLIB schema is a copy of the standard schema used for testing purposes only.

Overview¶

Property	Value
Purpose	Testing and development
Status	May not be stable
Use Case	Internal testing only

⚠️ Warning: This schema is for testing purposes only and should not be used for actual data annotation.

Schema format comparison¶

All schemas are available in four equivalent formats:

Format	Extension	Use Case	Editing
XML	`.xml`	Tool validation and analysis	❌ Never edit directly
MEDIAWIKI	`.mediawiki`	Human-readable, schema development	✅ Primary editing format
JSON	`.json`	AI tools, easy lookup	❌ Generated from XML/MEDIAWIKI
TSV	`.tsv`	Spreadsheet editing, ontology mapping	⚠️ Good for adding references

Conversion between formats¶

Use the HED online tools or command-line tools:

# Install HED Python tools 
pip install hedtools
# Convert schema
hedpy schema convert path/to/schema.mediawiki

Using schemas in your data¶

HED requires that you specify a HED version for most operations.

BIDS datasets¶

In BIDS, the dataset_description.json located at the top level of the directory containing a dataset has the version.

BIDS dataset using the standard schema

{
  "Name": "My Dataset",
  "BIDSVersion": "1.9.0",
  "HEDVersion": "8.4.0"
}

BIDS dataset using two non-conflicting library schemas

{
  "Name": "My Dataset",
  "BIDSVersion": "1.9.0",
  "HEDVersion": ["score_2.1.0", "lang_1.1.0"]
}

In this example the specified SCORE and LANG versions do not conflict and partner with the same HED standard schema (8.4.0), so they can be used together without namespace prefixes.

Programmatic access¶

Accessing the schema in Python

from hed import load_schema_version
schema = load_schema_version('8.4.0')

The HED schemas are cached in the Python HEDTools. Pass the schema object as needed.

The MATLAB HEDTools provide two ways of analyzing HED, both of which rely on an underlying Python HEDTools for their implementation: calls to web services and direct installation. Both approaches use MATLAB wrappers, so no knowledge of Python is required. The web services method requires no installation except for adding the tools to the MAtLAB path. The services are hosted at HED online tools. The other method involves direct calls to the Python HEDTools within MATLAB.

Direct calls to Python in MATLAB

MATLAB: Direct Python calls in MATLAB

hedTools = HedToolsPython('8.4.0');

The hedTools object, which provides wrappers to the main Python HEDTools operations, loads the schema internally. This usage requires that the Python HEDTools be installed in the MATLAB Python environment, which is probablematic for older versions of MATLAB. See MATLAB HEDTools for more information.

Direct calls to Python in MATLAB

import { buildSchema, SchemaSpec, SchemaSpecs } from '@hed-standard/hed-validator';
const spec1 = new SchemaSpec('', '8.4.0', '', '')
const specs = new SchemasSpec().addSchemaSpec(spec1)
const hedSchemas = await buildSchemas(specs)

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## Getting help

- **Schema questions**: [GitHub issues](https://github.com/hed-standard/hed-schemas/issues)
- **Technical support**: [hed.maintainers@gmail.com](mailto:hed.maintainers@gmail.com)
- **Documentation**: [hedtags.org](https://www.hedtags.org)
- **Community**: [HED Working Group](https://www.hedtags.org)