sexbase - Definition of supersets

Any number of extents can be defined as superset of an extent. Supersets must be defined as extents based on the same type as the current extent or on a base type of the current extent structure, in which case the superset must be weak-typed.

Subset/superset relations are bi-directional and need to be defined only in one direction. As long as the set relations are consistent, one may define also both directions.

An extent can be defined as the intersection of its supersets by setting the intersect option .