Discussion of "special" tags such as Event-context, Definition, Onset, and Offset.

[VisLab]

HED has some special tags. This discussion thread will try to explain some of them.

[VisLab]

Event-context

Event-context is a special HED tag, which at least currently, is never meant to be inserted by annotators. It is meant to be filled in by a future context mapper. Right now, if you use it, HED doesn't give an error. The tag has the topLevelTagGroup schema attribute which means that it has to be unnested in a tag group that is not nested. Definition, Onset, and Offset also have this condition. This attribute means that tag groups containing these tags cannot be nested. In other words, An Event-context tag group cannot contain another Event-context (or a Definition, Onset group or Offset group).

The purpose of the Event-context is to provide an anchor group for downstream tools to write context information (such as which events are ongoing or some relationship calculated from a previous event sequence) as tags into the tag string for analysis tools to use. This mapping has not yet been implemented in tools but is on the near-term to-do list after validation.
@MichaelJachan