11. The system of claim 10 , wherein assigning unique union identifiers to each of the union tuples belonging to the union relation comprises generating a union id relation for the union relation, wherein the union id relation defines uniquely identified union tuples that each assign a unique number to each of the union tuples.
11. The system of claim 10 , wherein assigning unique union identifiers to each of the union tuples belonging to the union relation comprises generating a union id relation for the union relation, wherein the union id relation defines uniquely identified union tuples that each assign a unique number to each of the union tuples. 12. The system of claim 11 , wherein generating a respective injector relation for each of the alternative subtypes comprises generating injector tuples by matching domain identifiers in a domain id relation for the alternative subtype to domain identifiers in a union id relation for the algebraic data type to determine domain tuples that should be paired with respective union identifiers in the injector tuples.