CS 4400 Chapter Notes - Chapter 15: Joule, Xu, Fifth Normal Form

• School: Georgia Tech
• Department: Computer Science
• Course: CS 4400
• Professor: monicasweat

Document Summary

Functional dependencies: inference rules, equivalence and minimal cover. Set of attributes x functionally determines a set of attributes y if the value of x determines a unique value y. X -> y holds if whenever two tuples have the same value for x, they must have the same value for y. X -> y in r specifies a constraint on all relation instances r( r) Fds are derived from the real-world constraints on the attributes. An fd x-> y is inferred from or implied by a set of dependencies f specified on r if x-> y holds in every legal relation state r of r. Given a set of fds f, we can infer additional fds that hold whenever the fds in f hold. Reflexive: if y subset-of x, then x -> y. Augmentation: if x -> y, then xz -> yz. Transitive: if x -> y and y -> z, then x -> z.