Module hdk::link

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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 are retrived from the DHT by performing link::get_links or link::get_link_details against the base of a link.

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.


An extension to obtain a link type filter.


Create a link from a base entry to a target entry, with an optional tag.
Delete a specific link creation record.
Get all link creates and deletes that reference a base entry hash, optionally filtered by type or tag.
Returns all links that reference a base entry hash, optionally filtered by link type and tag.