Difference between canonical cover and minimal cover

database database-normalization functional-dependencies
Mitch picture Mitch · Jun 15, 2011 · Viewed 9.9k times · Source

Apologies if this is a ridiculous question;

I've searched high and low for an answer with no avail.

I know how to calculate minimal cover;

ie ensure each functional dependency only has one attribute on the the RHS, remove extratraneous/redudant lhs attributes by calculating closure of each examining all FD's, seeing if any can be removed (again by calculating closure)

Is 'canonical' cover just another word for the same thing?

Answer

user3282136 picture user3282136 · Feb 7, 2014

A canonical cover is "allowed" to have more than one attribute on the right hand side. A minimal cover cannot. As an example, the canonical cover may be "A -> BC" where the minimal cover would be "A -> B, A -> C". That is the only difference.

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