Editing Fourth normal form (section)

==4NF in practice==
A 1992 paper by Margaret S. Wu notes that the teaching of database normalization typically stops short of 4NF, perhaps because of a belief that tables violating 4NF (but meeting all lower normal forms) are rarely encountered in business applications. This belief may not be accurate, however. Wu reports that in a study of forty organizational databases, over 20% contained one or more tables that violated 4NF while meeting all lower normal forms.<ref name="Wu">{{cite journal|first=Margaret S.|last=Wu|title=The Practical Need for Fourth Normal Form|journal=ACM SIGCSE Bulletin|volume=24|issue=1|date=March 1992|pages=19–23|doi=10.1145/135250.134515}}</ref>