Computer Sciene of Udayana State University

April 26, 2009

Fourth Normal Form (4NF) – MVD

Filed under: Computer Science — ignaga @ 1:23 AM

· MVD is a dependency caused

in most cases by having several multi-valued attributes in an 1NF relation.

Or, when a determinant, for example A, determines several sets of values (e.g. B and C) as shown below.1

  • MVD between attributes A, B, and C in a relation using the following notation:

A –> B

A –> C

2

· MVD can be further defined as being trivial or nontrivial.

MVD A –> B in relation R is defined as being trivial if (a) B is a subset of A or (b) A U B = R.

MVD is defined as being nontrivial if neither (a) nor (b) are satisfied.

Trivial MVD does not specify a constraint on a relation, while a nontrivial MVD does specify a constraint



Defined as a relation that is in BCNF and contains no nontrivial MVDs.

BranchNo –> Sname

BranchNo –> Oname

Decompose BranchStaffOwner into two tables

3

42

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