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We have an (over simplified) university database... Decompose into 4NF (and hence BCNF)

(a) What is 4NF?
(b) Identify a non-trivial functional dependency in the given relation.
(c) Explain the concept of BCNF.
(d) How would you decompose the given relation to achieve 4NF?

1 Answer

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Final answer:

4NF is a database normalization technique that eliminates redundant data and dependencies. Non-trivial functional dependency is when the determinant functionally determines the dependent attribute. BCNF is a higher level of database normalization that ensures no non-trivial dependencies. To achieve 4NF, the given relation would be decomposed by identifying and separating multi-valued dependencies.

Step-by-step explanation:

(a) What is 4NF?

4NF stands for Fourth Normal Form, which is a database normalization technique. It is an extension of third normal form (3NF) and is used to further eliminate redundant data and dependencies. In 4NF, a relation is in 4NF if and only if it is in BCNF (Boyce-Codd Normal Form) and there are no non-trivial multi-valued dependencies.

(b) Identify a non-trivial functional dependency in the given relation.

A non-trivial functional dependency is a dependency where the determinant functionally determines the dependent attribute, and removing any attribute from the determinant would break the dependency. For example, if we have a relation with the attributes Student_ID and Course_ID, where Student_ID uniquely determines Course_ID, this would be a non-trivial functional dependency.

(c) Explain the concept of BCNF.

BCNF stands for Boyce-Codd Normal Form, which is a higher level of database normalization. It deals with functional dependencies and ensures that there are no non-trivial dependencies between attributes. A relation is in BCNF if and only if every non-trivial functional dependency in the relation is a dependency on a candidate key.

(d) How would you decompose the given relation to achieve 4NF?

To decompose the given relation into 4NF, we would first identify all the multi-valued dependencies in the relation. Then, we would create separate relations for each multi-valued dependency. This process is known as normalization and helps in eliminating redundancy and improving data integrity.

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