Tuesday, September 19, 2017

What are the properties of Functional dependencies in canonical cover

What are the properties of canonical cover in DBMS? List down the properties that are to be held by set of FDs in a minimal cover, Discuss about the properties of canonical cover 

Properties of functional dependencies in canonical cover (minimal cover)

Canonical cover of a set of functional dependencies F is mentioned as Fc.

A canonical cover Fc of a set of functional dependencies F has the following properties;

1. Canonical cover Fc is equivalent to F.
F logically implies all dependencies in Fc and Fc logically implies all dependencies in F. 

2. Any functional dependency in Fc cannot be redundant. Fc is minimal set of FDs.

If we remove any functional dependency from Fc, then Fc will no longer be equivalent to F. Removal of any FD from Fc eliminates property 1.

3. The functional dependencies in Fc do not contain redundant attributes on either side.

If X is a set of attributes and Y is another set of attributes, then X → Y is a functional dependency. If X → Y is part of Fc, then removal of any attributes on either side of the functional dependency X → Y result in loss of equivalency between Fc and F.


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