HED governance and decision-making

Table of Contents

1. Introduction

2. HED mission statement

3. HED organizational structure

4. HED processes

5. Operational guidelines

6. License

7. Acknowledgments

1. Introduction

Hierarchical Event Descriptors (HED) is an open standard and supporting ecosystem for describing experimental events, conditions, and experiment organization in a format that is both human- and machine-readable to enable analysis, re-analysis, and meta/mega-analysis.

This document describes HED’s mission principles, scope, and organizational processes. See Brief history of HED for a discussion of HED origins and development. The HED project homepage is a good place to start for an overview of HED and links to major resources.

2. HED mission statement

  • To enable and support the storing and sharing of recorded data in a fully analysis-ready format for efficient and effective within and cross-study data search, summary, and analysis.

  • To make the process of annotation accessible and usable for the global neuroimaging and related communities.

  • To open opportunities for new types of analysis and automation.

3. HED organizational structure

Managing a standard and integrating it into an ecosystem of other standards and tools requires many types of skills and tasks. To this end, the HED community has a number of identified groups acting in concert to promote HED and achieve its goals as show in the following organization chart and detailed in the following sections. The arrows indicate lines of communication. Final decision-making is by consensus of the HED Working Group.






HED Scientific Advisory Board

Strategic planning

Scott Makeig


HED Working Group

Oversight and
day-to-day decisions

Kay Robbins
Scott Makeig


HED Library Development Teams

Library development issues

Dora Hermes
Tal Pal Attia


HED Maintainers

Repository management

Kay Robbins
Dung Truong


HED Outreach

Annotation assistance

Annalisa Salazar


If you have a question or wish to become more involved in the HED efforts, post an issue to the main HED issues forum or email hed.maintainers@gmail.com

HED Scientific Advisory Board

The HED Scientific Advisory Board includes senior members of the neuroimaging community whose role is to evaluate the needs of the user community and to suggest strategic directions for HED development. The initial membership of this committee was by invitation of the HED Working Group based on their involvement in major neuroinformatics efforts relevant to HED.

Additional/replacement members may be invited at the discretion of the HED Scientific Advisory Board with input from the HED Working Group.

HED Working Group

The HED Working Group is made up of volunteers committed to spearheading the development of HED. The HED Working Group is responsible for developing the detailed technical roadmap for HED development, including vetting library projects, suggesting and planning for releases of new HED features, revising the HED standard vocabulary, exploring integration with other standards and relevant repositories, and resolving conflicts.

While the HED Scientific Advisory Board is concerned with high-level strategic directions, the HED Working Group is concerned with the tactical planning of HED development. Any member of the HED community can propose an agenda item and attend a HED Working Group meeting to discuss the item. The HED Working Group currently meets twice a week and keeps a running agenda and minutes.

HED Library Development Teams

In recognition that a single standardized vocabulary cannot capture the relevant metadata for all subfields, HED supports/encourages the development of specialized vocabularies to support detailed annotation of experiments in specialized areas. These specialized vocabularies are called HED library schemas. Each library schema has its own HED Library Development Team to initially develop the schema and to update the schema as needs arise. The HED Maintainers are responsible for checking that proposed changes meet the requirements of HED, but the library schema developers are responsible for the vocabulary itself.

HED Maintainers

This volunteer group is responsible for maintaining the HED Organization GitHub site. The maintainers facilitate issue discussions in the various HED issue forums, review pull requests (PRs), do releases, and perform routine maintenance on the HED repositories.

HED Outreach

A central goal of HED is to facilitate the creation of a large corpus of standardized neuroimaging and behavioral datasets that have sufficient annotation to be understood by users and handled by analysis tools. To that end, significant thrust of the HED standards initiative is to help users learn to annotate and to promote good annotation and event reporting practices. If you have questions about how to annotate particular aspect of your data, Post an issue to hed-examples explaining the issue.

HED User Community

This group consists of individuals who have contributed to the HED community. If you make a contribution of any kind to the HED effort please email hed-maintainers with your name, GitHub ID, and contribution so that you can be recognized as part of our community.

Along with members of the preceding groups, this group comprises broadly any individual who has used or has interest in using HED. All members are invited and encouraged to join the HED User Community by supporting the project in one of the many ways

4. HED processes

The HED approach to standards development follows the principles of the Modern Paradigm for Standards developed by OpenStand:

  1. Respectful cooperation between standards organizations

  2. Adherence to fundamental principles of standards development:
    a. Due Process
    b. Broad Consensus
    c. Transparency
    d. Balance
    e. Openness

  3. Collective empowerment

  4. Availability

  5. Voluntary adoption

The foundation of HED decision-making is listening to all members of the HED Community and striving to achieve consensus on each level of the HED standard process.

The criteria for forming a new HED Library Schema Development Team is a statement of intent with defined scope, proposed name, members of the team.

The HED Working Group reviews the statement of intent to make sure that the scope is well-defined and that the library schema does not have significant overlap with existing schemas.

The actual development process is iterative and schemas are always initially in a prerelease format while community discussion and technical reviews are conducted. An official release entails creating a permanent copy on zenodo with a DOI as well as a permanent copy on hed-schemas. Once a schema version has been officially released, it cannot be changed, as tools use these released versions in computation.

5. Operational guidelines

There are several resources that can help a new user get started on the HED resources. The HED resources website contains links to all the HED informational and help materials.

Users are encouraged to post questions, suggestions, and discussion on the appropriate GitHub issues forum on the GitHub hed-standard organization site as indicated in the following table.

Issue/suggestion type

Issue forum


Main issue forum


Primary forum for schema development.
Any issue can be posted and will be redirected if needed.



Documentation corrections.
Questions on examples.
Help on annotation.



Clarification/suggestions on the
specification document and JSON tests.

Python codebase


Bug reports and feature requests.

JavaScript codebase


Bug reports and feature requests.

HED also has a HED discussion group. Subscribe by emailing: hed-discussion+subscribe@googlegroups.com.

If you do not feel comfortable asking your question publicly or have a concern please feel free to email the HED maintainers at hed.maintainers@gmail.com.

How to propose a library schema.

Anyone can propose a HED library schema. As early as possible in the process, a member of the library schema development team should post an issue to the hed-schemas GitHub repository indicating the proposed library name, team members (with GitHub usernames), and brief description to start the open process development.

Alternatively, an interested user can post an GitHub issue to inquire about user interest and the HED Working Group can publicize the potential development and ask for participation to get things started. This process and schema design guidelines are described in the HED schema developer’s guide.

All HED community members are required to follow the HED Code of conduct. Please contact the HED maintainers at hed.maintainers+coc@gmail.com if you have any concerns or would like to report a violation.

6. License

To the extent possible under the law, the authors have waived all copyright and related or neighboring rights to the HED project governance and decision-making document, as per the CC0 public domain dedication / license.

7. Acknowledgments

We gratefully acknowledge the BIDS Community for providing an inclusive and balanced model of open-standard development. HED has borrowed heavily from BIDS in developing a working governance model to guide its evolution.

This document draws from the Modern Paradigm for Standards and from other open-source governance documents.