Source:- stackoverflow
The disjoint rule states an entity instance of a supertype can only be a member of one subtype. The overlap rule states an entity instance of a supertype can be a member of multiple subtypes.
Example of disjoint rule: Instance of Super-type Animal can only be member of exactly one of these Sub-types being Panda, Cheetah and Dog Disjoint Union , (An animal can either be Panda or be Dog or be Cheetah but can't be any two or more at the same time)
Example of overlap rule: Instance of Super-type Person can be member of multiple Sub-types being Woman, Driver and Engineer Overlapping Union , (A person can be a Woman and that same Woman can be Driver and that same Woman can be Engineer at the same time)
