Issue No.09 - September (1987 vol.13)
S. Jajodia , Computer Science and Systems Branch, Naval Research Laboratory
Let R be a ?-acyclic relational scheme, and let F be the set of functional dependencies (FD's) embodied in R. Given an existence constrained database r over R, it was shown in  that it is possible to connect tuples from different relations in r and construct a universal instance L, possibly containing null values d, such that the total projection of L onto R yields exactly the set r. Moreover, conditions were given which guarantee that this L would satisfy the functional dependency with nulls (NFD) counterparts of FD's, in F. The purpose of this note is to generalize the latter result and show that under the same conditions, L actually satisfies NFD counterparts of FD's in the closure F+ of F.
universal instance, Functional dependency with nulls, ?-acyclic relational scheme, representative instance
S. Jajodia, "An Extension of "Representative Instances and ?-Acyclic Relational Schemes"", IEEE Transactions on Software Engineering, vol.13, no. 9, pp. 1047-1048, September 1987, doi:10.1109/TSE.1987.233792