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Please use this identifier to cite or link to this item: http://hdl.handle.net/2451/14613

Authors: Vassiliou, Yannis
Issue Date: Oct-1980
Publisher: Stern School of Business, New York University
Series/Report no.: IS-81-08
Abstract: Functional dependencies play an important role in relational database design. They are defined in the context of a single relation which at all times must contain tuples with non-null entries. In this paper we examine an extension of the functional dependency interpretation to handle null values, that is, entries in tuples that represent incomplete information in a relational database. A complete axiomatization of inference rules for extended functional dependencies is also presented. Only after having such results is it possible to talk about decompositions and normalization theory in a context of incomplete information. Finally, we show that there are several practical advantages in using nulls and a weaker notion of constraint satisfiability.
URI: http://hdl.handle.net/2451/14613
Appears in Collections:IOMS: Information Systems Working Papers

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