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Generalized Dependencies in Relational Databases
Attila Sali Sr. 3, Attila Sali 4 5
Abstract
A new type of dependencies in a relational database model introduced in is investigated. If b is an attribute, A is a set of attributes then it is said that b (p,q)-depends on A, in notation A® b, in a database relation r if there are no q+1 tuples in r such that they have at most p different values in each column of A, but q+1 different values in b. (1,1)-dependency is the classical functional dependency. Let \cal J(A) denote the set {b\colon A®b}. The set function \cal J\colon 2W ®2W becomes a closure if p = q. Results on representability of closures by (p,p)-dependencies are presented.
Keywords: relational database, closure, functional dependency, branching dependency, balanced graph
Footnotes:
1 AMS Subject classification Primary 68P15 68R05 Secondary 05D05
2 AMS Subject classification Primary 68P15 68R05 Secondary 05D05
3 Informatics Centre of Semmelweis University of Medicine Budapest, Kálvária tér 5. H-1089 HUNGARY
4 The work of the second author was supported by the Hungarian National Foundation for Scientific Research grant numbers T016389, and 4267, and European Communities (Cooperation in Science and Technology with Central and Eastern European Countries) contract number CIPACT930113
5 Corresponding author. e-mail:sali@math-inst.hu Mathematical Institute of HAS, Budapest P.O.B. 127 H-1364 HUNGARY