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:
“We are playing with fire when we skip the years of three, four, and five to hurry children into being age six.... Every child has a right to his fifth year of life, his fourth year, his third year. He has a right to live each year with joy and self-fulfillment. No one should ever claim the power to make a child mortgage his today for the sake of tomorrow.”
—James L. Hymes, Jr. (20th century)
“Perhaps the feelings that we experience when we are in love represent a normal state. Being in love shows a person who he should be.”
—Anton Pavlovich Chekhov (1860–1904)
“Cruelty has a Human Heart,
And jealousy a Human Face;
Terror the Human Form Divine,
And secrecy the Human Dress.”
—William Blake (1757–1827)