This preview shows page 1. Sign up to view the full content.
University of Waterloo
School of Computer Science
CS348
Spring 2009
Assignment 6
Due: July 14, 2009
1.
30%(a) Let F = {AB
→
C, A
→
D, BD
→
C, C
→
A} be the set of fd’s on R(ABCD).
Find all candidate keys of R.
Explain your answer.
To find all keys, enumerate all possible subsets and test for minimality and that the
subset determines all attributes in R.
With the help of the closure algorithm for a set
of attributes, the students need to show that BD,BC,AB are the keys and are the
only
keys.
70%(b) Let S={AB,BCD,AD} be a decomposition of R. For each relation scheme in S,
find all projected fd’s.
Is S in 3NF? Is S in BCNF? Is S a lossless decomposition? Is S
dependency preserving? Explain your answers.
20% To find all nontrivial projected fd’s, consider all possible fd’s defined on the
corresponding relation scheme. That is, the students need to show that they consider
all possible nontrivial fd’s X
→
A and see if they are in the closure of F.
AB: no nontrivial fd.
This is the end of the preview. Sign up
to
access the rest of the document.
 Spring '09
 Woody
 Computer Science

Click to edit the document details