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Towards computing revised models for FO theories
 in INAP
, 2009
"... Abstract. In many reallife computational search problems, one is not only interested in finding a solution, but also in maintaining it under varying circumstances. E.g., in the area of network configuration, an initial configuration of a computer network needs to be obtained, as well as a new confi ..."
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Abstract. In many reallife computational search problems, one is not only interested in finding a solution, but also in maintaining it under varying circumstances. E.g., in the area of network configuration, an initial configuration of a computer network needs to be obtained, as well as a new configuration when one of the machines in the network breaks down. Currently, most such revision problems are solved manually, or with highly specialized software. A recent declarative approach to solve (hard) computational search problems involving a lot of domain knowledge, is by finite model generation. Here, the domain knowledge is specified as a logic theory T, and models of T correspond to solutions of the problem. In this paper, we extend this approach to also solve revision problems. In particular, our method allows to use the same theory to describe the search problem and the revision problem, and applies techniques from current model generators to find revised solutions. 1
Grounding FO(ID) with Bounds
"... Abstract. Grounding is the task of reducing a given firstorder theory T and finite domain to an equivalent propositional theory. It is used as preprocessing step in many logicbased reasoning systems. In this paper, we present a method to improve grounding for FO(ID), the extension of firstorder l ..."
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Abstract. Grounding is the task of reducing a given firstorder theory T and finite domain to an equivalent propositional theory. It is used as preprocessing step in many logicbased reasoning systems. In this paper, we present a method to improve grounding for FO(ID), the extension of firstorder logic with inductive definitions. The method consists of computing bounds for subformulas of T, indicating for which part of the given domain, the truth value of their subformula is the same in every model of T. Bounds can be used to efficiently produce compact groundings. We present both theoretical results and experiments to support this claim. 1
Inductive Definitions in Constraint Programming
"... Constraint programming (CP) and answer set programming (ASP) are two declarative paradigms used to solve combinatorial problems. Many modern solvers for both these paradigms rely on partial or complete Boolean representations of the problem to exploit the extremely efficient techniques that have bee ..."
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Constraint programming (CP) and answer set programming (ASP) are two declarative paradigms used to solve combinatorial problems. Many modern solvers for both these paradigms rely on partial or complete Boolean representations of the problem to exploit the extremely efficient techniques that have been developed for solving propositional satisfiability problems. This convergence on a common representation makes it possible to incorporate useful features of CP into ASP and vice versa. There has been significant effort in recent years to integrate CP into ASP, primarily to overcome the grounding bottleneck in traditional ASP solvers that exists due to their inability to handle integer variables efficiently. On the other hand, ASP solvers are more efficient than CP systems on problems that involve inductive definitions, such as reachability in a graph. Besides efficiency, ASP syntax is more natural and closer to the mathematical definitions of such concepts. In this paper, we describe an approach that adds support for answer set rules to a CP system, namely the lazy clause generation solver chuffed. This integration also naturally avoids the grounding bottleneck of ASP since constraint solvers natively support finite domain variables. We demonstrate the usefulness of our approach by comparing our new system against two competitors: the stateoftheart ASP solver clasp, and clingcon, a system that extends clasp with CP capabilities.