HED specification

Welcome to the official specification for Hierarchical Event Descriptors (HED), a system for annotating events and experimental structure using controlled vocabularies.

About HED

HED (Hierarchical Event Descriptors) is a system for annotating events and experimental structure using controlled vocabularies. The HED ecosystem includes:

  • Vocabularies - Standardized terms organized in hierarchical schemas

  • Annotation tools - Software for creating and validating HED annotations

  • Analysis tools - Methods for searching and analyzing HED-annotated data

  • Community schemas - Domain-specific extensions to the base vocabulary

Specification contents

1. Introduction

Introduction to HED - Overview of the HED system and its applications.

Topics:

  • HED system overview

  • Integration with neuroimaging standards

  • Schema vocabulary

  • Getting started

2. Terminology

Terminology - Key concepts and definitions used throughout the specification.

Topics:

  • Character sets and restrictions

  • HED vocabulary terminology

  • Schema version naming

  • Tag specification

3. HED formats

HED formats - Schema and annotation format specifications.

Topics:

  • Schema format

  • HED string format

  • Sidecar format

  • Assembly and validation

4. Basic annotation

Basic annotation - Fundamental annotation techniques and best practices.

Topics:

  • Annotation principles

  • Basic event markup

  • Event context

  • Temporal relationships

5. Advanced annotation

Advanced annotation - Complex annotation patterns and advanced features.

Topics:

  • Definitions

  • Temporal scope

  • Event structure

  • Advanced examples

6. Infrastructure and tools

Infrastructure and tools - HED ecosystem tools and services.

Topics:

  • HED tools overview

  • Validation services

  • Web-based tools

  • Programming interfaces

7. Library schemas

Library schemas - Domain-specific schema extensions.

Topics:

  • Library schema concept

  • Creating library schemas

  • Using library schemas

  • BIDS integration

8. HED ontology

HED ontology - Ontological framework and mappings.

Topics:

  • Ontological foundations

  • Semantic relationships

  • External ontology mappings

  • Interoperability

Appendices