HED (Hierarchical Event Descriptors) is a standardized vocabulary and supporting infrastructure for annotating experimental metadata and mapping it into the experimental timeline. See HED resources for more information about the HED project.

HED itself consists of a standard vocabulary the (HED standard schema) and specialized subfield vocabularies (HED library schemas). These vocabularies are developed and maintained in the hed-schemas GitHub repository.

The HED ontology is a representation of the HED schemas as a formal ontology of the HED information space. Releases of new HED schemas trigger a generation of a new HED ontology in this repository (hed-ontology), and maintainers of this repository do a new release. The correspondence between the HED schemas and HED ontology is explained more fully in The HED ontology chapter of the **hed-specification.

Each HED entity in the HED information space has a globally unique identifier of the form HED_xxxxxxx where xxxxxxxx is a 7-digit number.

The identifier namespace is assigned as follows:

These are the PURL values relative to the

In general, posts to our GitHub issue tracker are recommended, however, if needed, you can contact the ontology curator by sending an e-mail mailto:[email protected].