Fourth Normal Form (4NF)
Fourth normal form eliminates, on top of BCNF, non-trivial multivalued dependencies (MVD), preventing redundancy of multi-valued attributes.
Purpose
To handle many-to-many redundancy caused by multivalued dependencies and design cleaner table structures.
Mechanism
If A→→B and A→→C (multivalued dependencies) with B and C independent, split into (A,B) and (A,C). E.g., teacher→→courses and teacher→→skills: splitting avoids the courses×skills Cartesian redundancy.
Use cases
- Database design
- Multivalued dependency
- Advanced normalization