Part 3, "CQL Functions"... how to link to the functions resource?

[aaime]

When a server implements functions, it "SHALL support the HTTP GET operation at the /functions path."

Now, all resources are linked and this one should be linked from the landing page. But I cannot find a "rel" that should be used to link to functions.

In a similar way to how queryables are linked using the http://www.opengis.net/def/rel/ogc/1.0/queryables rel, I would expect to find a http://www.opengis.net/def/rel/ogc/1.0/functions rel for the functions resource... but the specification does not seem to contain one.