What is HED?
HED (Hierarchical Event Descriptors) is a framework for systematically describing both laboratory and real-world events. HED tags are comma-separated path strings. The goal of HED is to describe precisely the nature of the events of interest occurring in an experiment using a common structured vocabulary and standardized tools. The HED framework has been developed for neurological imaging data (e.g., EEG, MEG, iEEG, fMRI), physiological (e.g., ECG, EMG, GSR) as well as multimodal experiment (e.g., mobile brain/body imaging). HED has been adopted as part of the BIDS (http://bids.neuroimaging.io) standard for brain imaging. The HED standards group maintains the HED schema and tools at https://github.com/hed-standard. The HED schema can be viewed using the HED viewer.
HED schema generations (3G versus 2G)
HED (starting with HED schema version 8.0.0) uses a new more powerful framework for annotation, known as HED-3G or HED third generation. Schema versions earlier than 8.0.0 use a less powerful framework (known as HED-2G) and will be deprecated in the coming year. You should always use HED schema versions HED 8.0.0 or greater for annotation.
HED online tools help
More detailed help on using these online tools is available at: [Help pages for online tools]
HED services help
The HED online tools are also available as callable web services. More detailed help on calling these services is available at: [Help pages for HED web services]
Downloadable examples of calling these services from a MATLAB program can be found at: [Github MATLAB examples]
Additional web-based tools are under development. All code is open-source and available in the hed-python repository on Github. For more information on HED, visit the documentation page.