3.1.12. Function dependency

  • Consider a relation schema R(A,B,C,D) and a set F of functional dependencies
    • Aim to find all keys (minimal superkeys),
    • by determining closures of all possible X subsets of R’s attributes, e.g.
      • A+, B+, C+, D+,
      • AB+, AC+, AD+, BC+, BD+, CD+
      • ABC+, ABD+, BCD+
      • ABCD+