Lossless, dependency preserving BCNF

Question

The following relations are given:

R1 = {A, B, C}

R2 = {C, D}

R3 = {D, E}

The task is to find a set of function dependencies to satisfy BCNF (lossless, and dependency preserving). I think that this is not possible here.

Without dependency preserving i got this:

A -> B, C

C -> A, D

D -> A, E

Is this correct and is it possible to find a dep. pres. set?

Thanks in advance.

Answer 1

I'm not sure I fully understand the question. But the simplest way to "manufacture" a relation in BCNF is to use one and only one single-attribute key. These functional dependencies

• A->BC
• C->D
• D->E

result in these relations.

• R _a { A BC}
• R _b { C D}
• R _c { D E}

R _a is in 5NF. The other two are in 6NF.