Let R (ABCDEFGH) be a relation schema and F be the set of dependencies 𝐹 =…

2022

Let R (ABCDEFGH) be a relation schema and F be the set of dependencies 𝐹 = {𝐴→𝐵,𝐴𝐵𝐶𝐷→𝐸,𝐸𝐹→𝐺,𝐸𝐹→𝐻 and 𝐴𝐶𝐷𝐹→𝐸𝐺}. The minimal cover of a set of functional dependencies is

  1. A.

    𝐴→𝐵,𝐴𝐶𝐷→𝐸,𝐸𝐹→𝐺, and 𝐸𝐹→𝐻

  2. B.

    𝐴→𝐵,𝐴𝐶𝐷→𝐸,𝐸𝐹→𝐺,𝐸𝐹→𝐻 and 𝐴𝐶𝐷𝐹→𝐺

  3. C.

    𝐴→𝐵,𝐴𝐶𝐷→𝐸,𝐸𝐹→𝐺,𝐸𝐹→𝐻 and 𝐴𝐶𝐷𝐹→𝐸

  4. D.

    𝐴→𝐵,𝐴𝐵𝐶𝐷→𝐸,𝐸𝐹→𝐻 and 𝐸𝐹→𝐺

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Correct answer: A

Compute the minimal cover for F = {A→B, ABCD→E, EF→G, EF→H, ACDF→EG}.

Step 1: Split right-hand sides so each dependency has a single attribute on the right.

  • A→B

  • ABCD→E

  • EF→G

  • EF→H

  • ACDF→E

  • ACDF→G

Step 2: Minimize left-hand sides by removing any extraneous attributes.

  1. Check ABCD→E: test if B is extraneous. Compute closure of {A,C,D}: A gives B (A→B), so {A,C,D}+ contains B, then ABCD→E yields E. Hence B is extraneous and ABCD→E reduces to ACD→E.

Step 3: Remove redundant dependencies.

  • ACDF→E is implied by ACD→E because ACDF contains ACD, so ACDF→E is redundant.

  • ACDF→G is implied as follows: ACDF gives E (via ACD→E) and with F present we have EF, and EF→G gives G. Thus ACDF→G is redundant.

Final minimal cover:

  • A→B

  • ACD→E

  • EF→G

  • EF→H

This matches the minimal cover provided in the correct option.

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