a set of Important Definitions 1. 0 satisfies A in I(F(I) A)iff I(A)(o)=T 2. A is satisfiable in I iff there is o E Xr such that (Z,0)A 3. A is satisfiable iff there is an interpretation in Which a is satisfiable 4. A is valid in I(FI A) iff for every assignment ∈∑x,F(x)A 5. A is valid iff a is valid in every interpretation 6. A is contradictory or unsatisfiable iff for every interpretation i and every assignment o T(A)()=F Logic in Computer Science -p8/18A set of Important Definitions 1. σ satisfies A in I (|=(I,σ) A) iff I(A)(σ) = T 2. A is satisfiable in I iff there is σ ∈ ΣI such that |=(I,σ) A. 3. A is satisfiable iff there is an interpretation in which A is satisfiable. 4. A is valid in I (|=I A) iff for every assignment σ ∈ ΣI, |=(I,σ) A. 5. A is valid iff A is valid in every interpretation. 6. A is contradictory or unsatisfiable iff for every interpretation I and every assignment σ, I(A)(σ) = F. Logic in Computer Science – p.8/18