2004 | OriginalPaper | Chapter
Weak Functional Dependencies in Higher-Order Datamodels
–The Case of the Union Constructor–
Authors : Sven Hartmann, Sebastian Link, Klaus-Dieter Schewe
Published in: Foundations of Information and Knowledge Systems
Publisher: Springer Berlin Heidelberg
Included in: Professional Book Archive
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We present an axiomatisation for weak functional dependencies, i.e. disjunctions of functional dependencies, in the presence of several constructors for complex values. These constructors are the tuple constructor, the set-constructor, an optionality constructor, and a union constructor. The theory is smooth and rather uniform, if the union-constructor is absent. Its presence, however, complicates all results and proofs significantly. The reason for this is that the union-constructor comes alomg with non-trivial restructuring rules. In particular, if the union-constructor is absent, a subset of the rules is complete for the implication of ordinary functional dependencies, but this does not hold, if the union constructor is present.