A collection of instances of type of collection type. type of collection type classified by disjointness is a collection of the three major types of CollectionTypes: type of collection is the most general type of type of collection and tells nothing about how the collections in the type are related (no disjointness restrictions). sibling disjoint collection type (a spec of type of collection) gives some disjointness constraints, but with some exceptions. disjoint classification scheme gives the most disjointness constraints--all instances of any instance of disjoint classification scheme must by disjoint collections. type of collection type classified by disjointness is in the KB to explicitly show how type of collection, sibling disjoint collection type, and disjoint classification scheme are related to anyone dealing with CollectionTypes. The facet assertion (faceted covering type of collection type of collection type classified by disjointness) states that any instance of type of collection should be checked for possible membership in sibling disjoint collection type or disjoint classification scheme.