INFS1603 Lecture Notes - Lecture 7: Functional Dependency, First Normal Form, Third Normal Form

• School: UNSW, UNSW Sydney
• Department: Information Systems
• Course: INFS1603
• Professor: All

Document Summary

F of is a set of given fds. F+ is the set of all implied fds. Fmin is the minimal set (minimal cover) of fds that is equivalent to f. this minimal set of fds as no redundancies. To (cid:272)o(cid:373)e f(cid:396)o(cid:373) a gi(cid:448)e(cid:374) set of f of fds to f+ o(cid:396) f(cid:373)i(cid:374), (cid:449)e use a(cid:396)(cid:373)st(cid:396)o(cid:374)g(cid:859)s i(cid:374)fe(cid:396)e(cid:374)(cid:272)e (cid:396)ules. This is an inference rule: a->b: read: a determines b; if a then b; if the premise a holds, then the conclusion b holds; b can be inferred from a; a implies b. I(cid:374) a (cid:396)elatio(cid:374) : a(cid:374) att(cid:396)i(cid:271)ute b is (cid:858)fu(cid:374)(cid:272)tio(cid:374)ally depe(cid:374)de(cid:374)t(cid:859) o(cid:374) a(cid:374) att(cid:396)i(cid:271)ute a if the (cid:448)alue of a u(cid:374)i(cid:395)uely determines the value of b. Ar(cid:373)stro(cid:374)g"s i(cid:374)fere(cid:374)ce rules: set of inference rules that can be used to infer all the fds based on a given set of. If y is a subset of x, then x->y.