问题
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?
回答1:
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.
回答2:
I believe that these are one in the same, but I looked it up to be sure. The goal in calculating the Canonical is to provide a minimum, in matters or redundancy.
Canonical
回答3:
canonical cover is to produce the minimal FD from the closure set F+ .The main factor of bring down for canonical closure is to ensure that there are no redundant dependencies in our database.
- divyalakshmi
来源：https://stackoverflow.com/questions/6356707/difference-between-canonical-cover-and-minimal-cover