Let be a relation
R(NameFile, Size, Directory, DateCreation,HourCreation,Login,AutAccess,DateAccess,TypeAcces
F={NF,D→S; NF, D →DC; NF, D→HC; L,NF,D→A; L,NF,D,DA,HA→TA; }
Part of the instances are given in the following array:
1. What are the minimal keys of R? Why?
2. In which normal type is R? Why?
I only know that:
- a key is minimal when every attributes that appears in no functional dependency is in every minimal keys
- Every attributes that appears only on the left of the FD is in every keys.
- Every attributes that appears only on the right of the DF isn't in any key.
Therefore we should have K1={NF,R,L,DA,HA}
as the only minimal key.
What type of Normal Form is relation R?
I know that
- something is 1NF if forall attributes of R, there is an atomic value
Therefore, it is at least 1NF,
something is 2NF iif:
- The scheme is at least 1NF
- Forall An attribute, not in any key, A doesn't depends to part of the key. that is to say not in any functional dependency.
A scheme of relation R is 3NF iif
- The scheme is 2NF
- Not exists a transitive functional dependency
But I don't know what to do from there... I don't even understand the two last definitions