Explain the structure of well formed formulae, Database Management System

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Explain the structure of well formed formulae in relational calculus.

Ans: a. An atom is a formula

b. If P1 is a formula, after that so are ¬P1 and (P1)

c. If P1 and P2 are formulae, after that so are P1 V P2, P1 ^ P2, P1 → P2

d. If P1(s) is a formula containing a free variable s and r is a relation after that

∃ s ε r (P1(s) ) and ∀ s ε r (P1(s)) are also formulae

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