Every entity or action definition from either input appears unchanged in the result.
The result declares exactly the entity types declared by either input.
The result declares exactly the action UIDs declared by either input.
Every action from either input keeps its ancestors in the result.
Every standard or external entity type from either input is standard or external in the result. In particular, an external entity type never links to an enumerated entity type.
The result never declares the entity type of an action as an entity type.
Every entity definition of the result is a definition from either input.
Every action entry of the result is that action's entry in either input.
An entity type's ancestors in the result are exactly the entity types reachable from it through the ancestors listed by either input.
The result keeps every declaration of either input.
A partial schema with closed ancestors that keeps the declarations of both inputs keeps the declarations of the result.
No entity type or action is defined by both inputs.
A well-formed partial schema links into the schema that completes it with
attributes attrs, when these are well-formed and lifted.
A well-formed partial schema links into its validation view.
Changing the input order does not change a successful link.
Changing the input order does not change whether linking fails.
Linking well-formed partial schemas produces a well-formed partial schema.
A complete link passes the existing schema well-formedness check.
Changing the grouping does not change a successful link.
Changing the grouping does not change whether linking fails.
A defined entity keeps its closed ancestor set after linking.