Minimal Cover for a Set of FDs
Minimal cover G for a set of FDs F:
- Closure of F = closure of G.
- Right hand side of each FD in G is a single attribute.
- If we modify G by deleting an FD or by deleting attributes from an FD in G, the closure changes.
Intuitively, every FD in G is needed, and ``as small as possible’’ in order to get the same closure as F.
e.g., A B, ABCD E, EF GH, ACDF EG has the following minimal cover:
- A B, ACD E, EF G and EF H
M.C. ??Lossless-Join, Dep. Pres. Decomp!!! (in book)