The listing of FD&C Act sections presented here identifies both the FD&C Act and U.S. Code section numbers, which can be used to narrow your search on the Law Revision Counsel website.

2025年1月21日 · The canonical cover of a set of functional dependencies F is a simplified version of F that retains the same closure as the original set, ensuring no redundancy. An attribute in a functional dependency is considered extraneous if it can be removed without altering the closure of the set of functional dependencies.

2013年11月7日 · Relation R(A,B,C,D,E,F) and FD’s A → BC and D → AF A→BC violates BCNF since A+ = ABC ≠ ABCDEF. So we split R into R1(ABC) and R2(ADEF). The only non-trivial FD in R1 is A→BC, and A+ = ABC, so R1 is in BCNF. R2 has a non-trivial dependency D→AF that violates BCNF because D+ = ADF ≠ ADEF. So we split R2 into R21(DAF) and R22(DE).

A set of attributes A is a key for a relation R if A functionally determines all attributes in R. Given a set S of FDs, we compute the closure of attribute set A using the FDs in S, then check if the closure is the set of all attributes in R. Eg. ABFG ABFG+ = ABCEFG; a key must functionally determine all attributes ABCDEFG.

Minimal Cover implies Lossless-Join, Defendency Preserving Decomposition. Notice that we have single attribute on the RHS in all FDs, we need to look for extraneous (redundant) attributes on the LHS and also look for FDs that are redundant. Where possible, apply Additivity rule (A’s axioms) remove “extraneous attributes” from each FD.

To search the FD&C Act on the Law Revision Counsel website, you may either search by U.S. code section number or browse the Title 21 section listing. Sec. 356. Expedited approval of drugs for...

In designing a database, for the purpose of minimizing redundancy, we need to collect a set F of functional dependencies (FD) that re ect the constraints of the underlying application. Ideally, we do not want to miss any FD, i.e., we want to obtain an F that is as large as possible. However, in practice, FD collection is a di cult process.

We denote the closure of F by F+. Basis: Y+:=Y. Induction: If X Y+, and X A is a given FD, then add A to Y+. End when Y+ cannot be changed. A+ = AB. C+=C. (AC)+ = ABCD. Other FD’s may follow logically from the given FD’s; these are implied FD’s. Motivation: Suppose we have a relation ABCD with some FD’s F.

Then, a derivation for f from F is a sequence of FDs with f as the last FD in the sequence such that any element in the sequence is either an element of. F or is an FD produced by the application of one of the Armstrong's axioms to FDs earlier in the sequence. R.

Given a set F of FDs, and a set X of attributes, the closure set of X (w.r.t F), denoted X+, is the set of all attributes that can be inferred to be functionally dependant on X. Surely X is a subset of X + .