Corrigendum to "On the undecidability of implications between embedded multivalued database dependencies" [Inform. and Comput. 122(1995) 221-235]
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By an implication for database dependencies we mean an expression H ⇒ F , where H is a conjunction of dependencies and F a single dependency. Fixing a class of such implications, a solution of the (finite) implication problem consists in an algorithmic procedure deciding for every implication in the class whether or not it holds in all (finite) databases (in which it is to be interpreted). In [3] this problem was studied for dependencies which are functional (fd) or embedded multivalued (emvd). As pointed out by Luc Segoufin, what was really shown is the following. Theorem 1. The implication problem and the finite implication problem for implicationsH ⇒ F , where F is an emvd and H a conjunction of emvds and fds, are unsolvable.
[1] Catriel Beeri,et al. The Implication Problem for Data Dependencies , 1981, ICALP.
[2] Catriel Beeri,et al. A Proof Procedure for Data Dependencies , 1984, JACM.
[3] Christian Herrmann. On the Undecidability of Implications Between Embedded Multivalued Database Dependencies , 1995, Inf. Comput..