Links in Holochain are analogous to a join table in a traditional SQL schema.
Links embody navigable graph structures between entires in a more general format than CRUD trees.
At a high level:
- Can implement direct or indirect circular references
- Have a base and target entry
- Can either exist or be deleted (i.e. there is no revision history, deleting removes a link permanently)
- Many links can point from/to the same entry
- Links reference entry hashes not actions
Links also support short (about 500 bytes) binary data to encode contextual data on a domain specific basis.
Links are not entries, there is only an action with no associated entry, so links cannot reference other links or maintain or participate in a revision history.