"A relation schema R* is in fourth normal form (4NF) if, whenever a nontrivial multivalued dependency X Y holds for R*, then so does the functional dependency X → A for every column name A of R*. Intuitively all dependencies are the result of keys." Fagin, Ronald. Multivalued Dependencies and a New Normal Form for Relational Databases(PDF). ACM Transactions on Database Systems. September 1977, 2 (1): 267. doi:10.1145/320557.320571. (原始内容(PDF)存档于2007-11-29).
ibm.com
almaden.ibm.com
"A relation schema R* is in fourth normal form (4NF) if, whenever a nontrivial multivalued dependency X Y holds for R*, then so does the functional dependency X → A for every column name A of R*. Intuitively all dependencies are the result of keys." Fagin, Ronald. Multivalued Dependencies and a New Normal Form for Relational Databases(PDF). ACM Transactions on Database Systems. September 1977, 2 (1): 267. doi:10.1145/320557.320571. (原始内容(PDF)存档于2007-11-29).
web.archive.org
"A relation schema R* is in fourth normal form (4NF) if, whenever a nontrivial multivalued dependency X Y holds for R*, then so does the functional dependency X → A for every column name A of R*. Intuitively all dependencies are the result of keys." Fagin, Ronald. Multivalued Dependencies and a New Normal Form for Relational Databases(PDF). ACM Transactions on Database Systems. September 1977, 2 (1): 267. doi:10.1145/320557.320571. (原始内容(PDF)存档于2007-11-29).