Chapter 7, Problem 28E

Explanation of Solution

To Compute B⁺:

• To compute B^+, the closure of an attribute “B” over a set of functional dependencies “F”, refer the algorithm in Figure 7.19 of the textbook.
• Consider the functional dependencies of Practice Exercises 7.6.
• Execute the algorithm to compute B⁺ for these functional dependencies.
  • The result is initialized to {B}.
  • For the first repetition,
    • Refer the functional dependency $\text{A}\to \text{BC}$ but here “A” is not a subset of {B}.
    • Refer the functional dependency $\text{CD}\to \text{E}$, but CD is not a subset of {B}