Database 1
Database Design
- Prof. dr. Paul M.E. De Bra
- Dept. of Computer Science
- Eindhoven Univ. of Technology
Redundancy of Inference Rules
- An inference rule r in a set of inference rules R for a type of constraints C is redundant if for all sets F of constraints of type C: F+{R-{r}} = F+
- Prove that none of the Armstrong rules are redundant in the set of (3) Armstrong rules.
- Prove that adding the union rule, the decomposition rule or the pseudotransitivity rule would make the set of rules redundant.
Inclusion Dependencies
- Let X = (A1, ..., An) and Y = (B1, ... , Bn) be sequences of attributes of R. The inclusion dependency X Yholds in R if and only if in each legal instance r for R:
- t1 r, t2r, i in 1..n: t1[Ai] = t2[Bi]
- A simple inclusion dependency A B met A, B R holds in R if and only if in each legal instance r for R:
- t1r, t2r: t1[A] = t2[B]
- Give inference rules for ids and sids and prove that they are correct.
Preparation for labsession 2
- Study chapter 7 of the database book, up to and including section 7.3.4.
- Section 7.3.4 explains the notion of canonical cover. It deals with reducing the size of sets of functional dependencies to verify.