Fourth normal form (4NF) is a normal form used in database normalization. Introduced by Ronald Fagin in 1977, 4NF is the next level of normalization after Boyce–Codd normal form (BCNF). Whereas the second, third, and Boyce–Codd normal forms are concerned with functional dependencies, 4NF is concerned with a more general type of dependency known as a multivalued dependency. A Table is in 4NF if and only if, for every one of its non-trivial multivalued dependencies X Y, X is a superkey—that is, X is either a candidate key or a superset thereof.
Read more about Fourth Normal Form: Multivalued Dependencies, Example, 4NF in Practice
Famous quotes containing the words fourth, normal and/or form:
“What, to the American slave, is your Fourth of July? I answer: A day that reveals to him, more than all other days in the year, the gross injustice and cruelty to which he is the constant victim. To him your celebration is a sham.”
—Frederick Douglass (c.1817–1895)
“Cant is always rather nauseating; but before we condemn political hypocrisy, let us remember that it is the tribute paid by men of leather to men of God, and that the acting of the part of someone better than oneself may actually commit one to a course of behaviour perceptibly less evil than what would be normal and natural in an avowed cynic.”
—Aldous Huxley (1894–1963)
“It is absolutely impossible to transcend the laws of nature. What can change in historically different circumstances is only the form in which these laws expose themselves.”
—Karl Marx (1818–1883)