20. The medium of claim 18 , wherein at least one constraint for preserving referential integrity specified by the constraint specification is based on dependence of values for a field of the second dataset on values for a field of the first dataset.
20. The medium of claim 18 , wherein at least one constraint for preserving referential integrity specified by the constraint specification is based on dependence of values for a field of the second dataset on values for a field of the first dataset. 21. The medium of claim 20 , wherein the field of the first dataset is a primary key and the field of the second dataset is a foreign key that references the primary key.