Can there be multiple minimal covers?

Can there be multiple minimal covers?

So we have 4 possible minimal covers: b->c, g->c OR g->e, b->d OR b->g, g->b, e->a . The correct answer is g–>c; g–>e; b–>g; e–>a; g–>b; g–>d according to this tool.

How do you calculate minimal cover?

Simple properties/steps of minimal cover:

1. Right Hand Side (RHS) of all FDs should be single attribute.
2. Remove extraneous attributes. [What is extraneous attribute? Refer here].
3. Eliminate redundant functional dependencies.

What is a minimal cover?

A minimal cover is a cover for which removal of any single member destroys the covering property. For example, of the five covers of , namely , , , , and , only and. are minimal covers. Similarly, the minimal covers of are given by , , , , , , , and .

What is minimal cover of functional dependency?

A minimal cover of a set of functional dependencies (FD) E is a minimal set of dependencies F that is equivalent to E. We cannot replace any dependency X->A in F with a dependency Y->A, where Y is a proper subset of X, and still have a set of dependencies that is equivalent to F.

Is minimal cover same as canonical cover?

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.

Are minimal covers unique?

No, it cannot be a canonical cover for your set of functional dependencies (FD). A canonical cover of F is a “minimal” set of functional dependencies equivalent to F, having no redundant dependencies or redundant parts of dependencies.

What is a reduced minimal cover?

A minimal cover is a simplified and reduced version of the given set of functional dependencies. Since it is a reduced version, it is also called as Irreducible set. It is also called as Canonical Cover. Steps to Find Minimal Cover. 1) Split the right-hand attributes of all FDs.

Why is canonical cover not unique?

No, it cannot be a canonical cover for your set of functional dependencies (FD). A canonical cover of F is a “minimal” set of functional dependencies equivalent to F, having no redundant dependencies or redundant parts of dependencies. The canonical cover you suggest is not equivalent to F .

How do I get a canonical cover?

Steps to find canonical cover:

1. There are two functional dependencies with the same set of attributes on the left:
2. There is an extraneous attribute in AB C because even after removing AB C from the set F, we get the same closures.
3. C is an extraneous attribute in A BC, also A B is logically implied by A B and B.

Is minimal and canonical cover same?

Does a set of FD’s have a unique canonical cover?