Skolem Function Continuation for Quantified Boolean Formulas

Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 10375)


Modern solvers for quantified Boolean formulas (QBF) not only decide the satisfiability of a formula, but also return a set of Skolem functions representing a model for a true QBF. Unfortunately, in combination with a preprocessor this ability is lost for many preprocessing techniques. A preprocessor rewrites the input formula to an equi-satisfiable formula which is often easier to solve than the original formula. Then the Skolem functions returned by the solver represent a solution for the preprocessed formula, but not necessarily for the original encoding.

Our solution to this problem is to combine Skolem functions obtained from a \(\mathsf {QRAT}\) trace as produced by the widely-used preprocessor Bloqqer with Skolem functions for the preprocessed formula. This approach is agnostic of the concrete rewritings performed by the preprocessor and allows the combination of Bloqqer with any Skolem function producing solver, hence realizing a smooth integration into the solving tool chain.


Conjunctive Normal Form Boolean Formula Propositional Formula Tool Chain Bound Model Check 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



We would like to thank Luca Pulina for providing us with the list of satisfiable instances of the QBF Eval 2016.


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Copyright information

© Springer International Publishing AG 2017

Authors and Affiliations

  1. 1.Johannes Kepler UniversityLinzAustria
  2. 2.The University of Texas at AustinAustinUSA

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