Self-description: the meta-schema is a valid instance of itself. schema matches its own union variant (anyOf). The items in its anyOf match its include variant, and the schemas those items name match the other variants. The schema language shows the check.

See also

Variant: the members of the meta-schema union.

Fixpoint problem: why that self-reference has to be a name.

References and naming: why the meta-schema is the axiom of the system.