Transformation of Database Management System with the Integration of 4th Normal Form
Achieving Fourth Normal Form (4NF) in Relational Database Design
In the world of relational databases, the Fourth Normal Form (4NF) plays a crucial role in maintaining data integrity and eliminating redundancy. To understand 4NF, it's essential to recognize and address Multivalued Dependencies (MVDs).
Recognizing Multivalued Dependencies (MVDs)
A Multivalued Dependency (MVD) occurs when an attribute determines multiple independent values of another attribute in a relation. For example, in a table with attributes Course, Instructor, and Textbook_author, a course can have multiple instructors and multiple textbook authors independently.
MVDs require the table to have at least three attributes, and the values dependent on the given attribute (e.g., Instructor and Textbook_author) must be independent of each other.
Conditions for Fourth Normal Form (4NF)
To be in 4NF, a relation must already be in Boyce-Codd Normal Form (BCNF). It must also have no non-trivial multivalued dependencies other than those based on a candidate key. If a multivalued dependency violates these rules, the relation is not in 4NF.
Solving MVDs to Achieve 4NF
- Identify Multivalued Dependencies: Analyze the relation for attributes where multiple independent sets of values exist corresponding to the same key.
- Decompose the Relation: Split the original relation into two or more relations to eliminate the independent MVDs. Each new table contains the key attribute and one of the multivalued attributes.
- Establish Relationships Using Foreign Keys: Use foreign keys to maintain relationships between the decomposed tables.
- Example Resolution:
The original table with MVDs:
| Course | Instructor | Textbook_author | |--------|------------|-----------------| | CS101 | Smith | Brown | | CS101 | Jones | Brown | | CS101 | Smith | Davis | | CS101 | Jones | Davis |
Splitting into two tables eliminates the MVD:
- Course_Instructors
| Course | Instructor | |--------|------------| | CS101 | Smith | | CS101 | Jones |
- Course_Textbook_Authors
| Course | Textbook_author | |--------|-----------------| | CS101 | Brown | | CS101 | Davis |
This adjustment removes redundancy caused by independently varying attributes, ensuring the relation is in 4NF.
Key Points and Benefits of 4NF
- 4NF prevents redundancy and update anomalies caused by multivalued dependencies.
- Decomposition is lossless and preserves dependencies.
- Tables achieve higher data integrity and consistency.
- It is particularly useful when a relation involves multiple independent multivalued attributes.
By following these steps, you can transform a non-4NF table into a well-structured, efficient, and consistent 4NF database, ensuring cleaner data and easier management.
In the process of addressing Multivalued Dependencies (MVDs) to achieve Fourth Normal Form (4NF), it's essential to first analyze a relation for attributes where multiple independent sets of values exist corresponding to the same key (such as Instructor and Textbook_author in a Course, Instructor, and Textbook_author table). Once MVDs are identified, the relation can be decomposed into two or more relations using foreign keys to maintain relationships between them, ensuring the removed redundancy caused by independently varying attributes, which is a key benefit of 4NF in technology and science-related fields.
