Currently sling:resourceSuperType properties are only evaluated in the Sling Servlet Resolver and it is only possible to retrieve the super type of a given type (via Resource.getResourceSuperType() (https://issues.apache.org/jira/browse/SLING-278) but not vice versa.
For the use case of e.g. searching for content of resource type a or any type derived from a it is necessary to know all resource types derived from a (direct or transitive) up front.
For that I propose to extend the ResourceResolver interface with an additional method which retrieves all derived resource types for a given type.
There was an initial discussion about this in https://firstname.lastname@example.org/msg73080.html.