Part of Stem. This page defines the link kind literal union used by link and link rule.

A link kind names what an edge means, and from the kind alone a peer knows whether the target must be fetched first, kept, shown, or merely cited.

Values and flags

kind	meaning	dependency	authority	placement	presentation	reference	retained
`dep`	state dependency: Change deps, Node heads and snapshot, Snapshot prev, Node prev	yes					yes
`proof`	the Grant or Group a blob relies on		yes				yes
`parent`	the parent node named by a Node blob			yes
`schema`	the schema or kind a blob declares				yes
`file`	a file or media blob the state embeds				yes		yes
`embed`	another resource shown inside this one				yes
`link`	an ordinary hyperlink					yes
`mention`	an inline reference to an account or resource					yes
`target`	the resource this one is about					yes

Dependency links are fetched and applied before the source can be applied. Authority links are fetched first of all. Placement links build the tree. Presentation links are fetched for a full rendering but their absence does not block applying the source. Reference links are indexed as citations and backlinks and drive notifications; target also drives the target access mode. Retained means a following peer keeps the target as long as it keeps the source.

Rules

The flags are fixed per kind so that every peer agrees without exchanging rule tables. Adding a kind is a protocol change to this union and its flags. Which fields of a state produce which kind is declared per Kind by link rules, except dep, parent and proof, which the handler always emits from the Node, Change, Snapshot and Grant fields themselves.

Today (HM24)

The blob_links and resource_links tables hold edges typed by strings such as change/dep, ref/head, comment/target, doc/Embed, metadata/icon, and the visibility propagation rules are a separate table of which edges carry visibility. The nine kinds replace both, and the Stem pages Links and The runtime model explain what sync and retention do with them.

Example

"dep"

Values and flags

Rules

Today (HM24)

Example

See also