Embodiments define a set of rules such that a type designer can express as part of a type's definition whether the type has extended the logic and/or constraints of its ancestral types in such a way that applications written against that ancestral type will continue to function correctly. Nonconformity can also be indicated and an embodiment can enforce limitations on a set of operations that can be performed on such instances when treated as their ancestral types. Applications can use standard interfaces to discover from embodiments whether such limitations can be in force for a particular instance and provide a user experience that accounts for those limitations. Embodiments can also provide mechanisms to enable type designers to limit a degree of extensibility for both types and/or Items.