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2007
IEEE

Symmetric Datalog and Constraint Satisfaction Problems in Logspace

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Symmetric Datalog and Constraint Satisfaction Problems in Logspace
We introduce symmetric Datalog, a syntactic restriction of linear Datalog and show that its expressive power is exactly that of restricted symmetric monotone Krom SNP. The deep result of Reingold [17] on the complexity of undirected connectivity suffices to show that symmetric Datalog queries can be evaluated in logarithmic space. We show that for a number of constraint languages Γ, the complement of the constraint satisfaction problem CSP(Γ) can be expressed in symmetric Datalog. In particular, we show that if CSP(Γ) is first-order definable and Λ is a finite subset of the relational clone generated by Γ then ¬CSP(Λ) is definable in symmetric Datalog. Over the two-element domain and under a standard complexity-theoretic assumption, expressibility of ¬CSP(Γ) in symmetric Datalog corresponds exactly to the class of CSPs solvable in logarithmic space. Finally, we describe a fairly general subclass of implicational (or 0/1/all) constraints for which the complement of the co...
László Egri, Benoit Larose, Pascal T
Added 04 Jun 2010
Updated 04 Jun 2010
Type Conference
Year 2007
Where LICS
Authors László Egri, Benoit Larose, Pascal Tesson
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