unions tests restriction facet in intervening union Types derived by restriction from a union type tests restriction facet in intervening union Types derived by restriction from a union type xsi:type used to name a member of a restricted union type Union of unions xsi:type used to name a member of a restricted union type tests restriction facet in intervening union tests restriction facet in intervening union tests restriction facet in intervening union Types derived by restriction from a union type xsi:type used to name a member of a restricted union type xsi:type used to name a member of a restricted union type xsi:type used to name a member of a restricted union type Union type a member of its own transitive membership Cyclicity of union types Cyclicity of union types Cyclicity of union types Cyclicity of union types