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STEPHAN KREUTZER COMPLEXITY OF MODEL-CHECKING PROBLEMS 10/81<br />

INTRODUCTION COMPLEXITY UPPER BOUNDS COMPOSITION LOCALITY LOCALISATION GRIDS GRID-LIKE MINORS LABELLED WEBS<br />

Complexity of First-Order Model-Checking<br />

Naïve algorithm gives running time and space:<br />

time: O(l · n m ) l: length of ϕ m: quantifier rank of ϕ<br />

space: O(m·log n) n: size of A<br />

Theorem: First-Order Model-Checking MC(FO) is PSPACE-complete.<br />

This is even true for MC(FO,A) for a fixed two element structure A.<br />

Proof. Reduction from satisfiability for Quantified Boolean Formulae<br />

Theorem. For any fixed ϕ,<br />

(data complexity)<br />

MC(ϕ, Str) ∈ AC 0 ⊆ LOGSPACE ⊆ PTIME<br />

However: Running time O(l · n m )

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