Results 1  10
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24
Sat encodings of statespace reachability problems in numeric domains
 In Proceedings of the 20th International Joint Conference on Artificial Intelligence (IJCAI07
, 2007
"... Translation to Boolean satisfiability is an important approach for solving statespace reachability problems that arise in planning and verification. Many important problems, however, involve numeric variables; for example, C programs or planning with resources. Focussing on planning, we propose a m ..."
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Cited by 16 (2 self)
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Translation to Boolean satisfiability is an important approach for solving statespace reachability problems that arise in planning and verification. Many important problems, however, involve numeric variables; for example, C programs or planning with resources. Focussing on planning, we propose a method for translating such problems into propositional SAT, based on an approximation of reachable variable domains. We compare to a more direct translation into “SAT modulo theory” (SMT), that is, SAT extended with numeric variables and arithmetic constraints. Though translation to SAT generates much larger formulas, we show that it typically outperforms translation to SMT almost up to the point where the formulas don’t fit into memory any longer. We also show that, even though our planner is optimal, it tends to outperform stateoftheart suboptimal heuristic planners in domains with tightly constrained resources. Finally we present encouraging initial results on applying the approach to model checking. 1
Stable models and difference logic
 Ann. Math. Artif. Intell
, 2008
"... on his 65th birthday The paper studies the relationship between logic programs with the stable model semantics and difference logic recently considered in the Satisfiability Modulo Theories framework. Characterizations of stable models in terms of level rankings are developed building on simple line ..."
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Cited by 11 (1 self)
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on his 65th birthday The paper studies the relationship between logic programs with the stable model semantics and difference logic recently considered in the Satisfiability Modulo Theories framework. Characterizations of stable models in terms of level rankings are developed building on simple linear integer constraints allowed in difference logic. Based on a characterization with level rankings a translation is devised which maps a normal program to a difference logic formula capturing stable models of the program as satisfying valuations of the resulting formula. The translation makes it possible to use a solver for difference logic to compute stable models of logic programs. 1
Boolean abstraction for temporal logic satisfiability
 IN DAMM AND HERMANNS [11
, 2007
"... Increasing interest towards property based design calls for effective satisfiability procedures for expressive temporal logics, e.g. the IEEE standard Property Specification Language (PSL). In this paper, we propose a new approach to the satisfiability of PSL formulae; we follow recent approaches t ..."
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Cited by 9 (3 self)
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Increasing interest towards property based design calls for effective satisfiability procedures for expressive temporal logics, e.g. the IEEE standard Property Specification Language (PSL). In this paper, we propose a new approach to the satisfiability of PSL formulae; we follow recent approaches to decision procedures for Satisfiability Modulo Theory, typically applied to fragments of First Order Logic. The underlying intuition is to combine two interacting search mechanisms: on one side, we search for assignments that satisfy the Boolean abstraction of the problem; on the other, we invoke a solver for temporal satisfiability on the conjunction of temporal formulae corresponding to the assignment. Within this framework, we explore two directions. First, given the fixed polarity of each constraint in the theory solver, aggressive simplifications can be applied. Second, we analyze the idea of conflict reconstruction: whenever a satisfying assignment at the level of the Boolean abstraction results in a temporally unsatisfiable problem, we identify inconsistent subsets that can be used to rule out possibly many other assignments. We propose two methods to extract conflict sets on conjunctions of temporal formulae (one based on BDDbased Model Checking, and one based on SATbased Simple Bounded Model Checking). We analyze the limits and the merits of the approach with a thorough experimental evaluation.
On handling distinct objects in the superposition calculus
 In Notes 5th IWIL Workshop
, 2005
"... Abstract. Many domains of reasoning include a set of distinct objects. For generalpurpose automated theorem provers, this property has to be specified explicitly, by including distinctness axioms. Since their number grows quadratically with the number of distinct objects, this results in large and ..."
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Cited by 8 (7 self)
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Abstract. Many domains of reasoning include a set of distinct objects. For generalpurpose automated theorem provers, this property has to be specified explicitly, by including distinctness axioms. Since their number grows quadratically with the number of distinct objects, this results in large and clumsy specifications, that may affect performance adversely. We show that object distinctness can be handled directly by a modified superpositionbased inference system, including additional inference rules. The new calculus is shown to be sound and complete. A preliminary implementation shows promising results in the theory of arrays. 1
On variableinactivity and polynomial Tsatisfiability procedures
, 2008
"... Verification problems require to reason in theories of data structures and fragments of arithmetic. Thus, decision procedures for such theories are needed, to be embedded in, or interfaced with, proof assistants or software model checkers. Such decision procedures ought to be sound and complete, to ..."
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Cited by 7 (6 self)
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Verification problems require to reason in theories of data structures and fragments of arithmetic. Thus, decision procedures for such theories are needed, to be embedded in, or interfaced with, proof assistants or software model checkers. Such decision procedures ought to be sound and complete, to avoid false negatives and false positives, efficient, to handle large problems, and easy to combine, because most problems involve multiple theories. The rewritebased approach to decision procedures aims at addressing these sometimes conflicting issues in a uniform way, by harnessing the power of general firstorder theorem proving. In this article, we generalize the rewritebased approach from deciding the satisfiability of sets of ground literals to deciding that of arbitrary ground formulæ in the theory. Next, we present polynomial rewritebased satisfiability procedures for the theories of records with extensionality and integer offsets. The generalization of the rewritebased approach to arbitrary ground formulæ and the polynomial satisfiability procedure for the theory of records with extensionality use the same key property – termed variableinactivity – that allows one to combine theories in a simple way in the rewritebased approach.
Theory decision by decomposition
, 2008
"... The topic of this article is decision procedures for satisfiability modulo theories (SMT) of arbitrary quantifierfree formulæ. We propose an approach that decomposes the formula in such a way that its definitional part, including the theory, can be compiled by a rewritebased firstorder theorem pro ..."
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Cited by 6 (5 self)
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The topic of this article is decision procedures for satisfiability modulo theories (SMT) of arbitrary quantifierfree formulæ. We propose an approach that decomposes the formula in such a way that its definitional part, including the theory, can be compiled by a rewritebased firstorder theorem prover, and the residual problem can be decided by an SMTsolver, based on the DavisPutnamLogemannLoveland procedure. The resulting decision by stages mechanism may unite the complementary strengths of firstorder provers and SMTsolvers. We demonstrate its practicality by giving decision procedures for the theories of records, integer offsets and arrays, with or without extensionality, and for combinations including such theories.
Satisfiability checking with difference constraints
 in IMPRS Computer Science, Saarbruceken
, 2005
"... This thesis studies the problem of determining the satisfiability of a Boolean combination of binary difference constraints of the form x − y ≤ c where x and y are numeric variables and c is a constant. In particular, we present an incremental and modelbased interpreter for the theory of difference ..."
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Cited by 5 (2 self)
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This thesis studies the problem of determining the satisfiability of a Boolean combination of binary difference constraints of the form x − y ≤ c where x and y are numeric variables and c is a constant. In particular, we present an incremental and modelbased interpreter for the theory of difference constraints in the context of a generic Boolean satisfiability checking procedure capable of incorporating interpreters for arbitrary theories. We show how to use the model based approach to efficiently make inferences with the option of complete inference.
Fully symbolic model checking for timed automata
 In Proc. of the Int’l Conf. on ComputerAided Verification (CAV), volume 6806 of Lecture Notes in Computer Science
, 2011
"... Abstract. In this paper we introduce a new formal model, called finite state machines with time (FSMT), to represent realtime systems. We present a model checking algorithm for FSMTs, which works on fully symbolic state sets containing both the clock values and the state variables. In order to veri ..."
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Abstract. In this paper we introduce a new formal model, called finite state machines with time (FSMT), to represent realtime systems. We present a model checking algorithm for FSMTs, which works on fully symbolic state sets containing both the clock values and the state variables. In order to verify timed automata (TAs) with our model checking algorithm, we present two different methods to convert TAs to FSMTs. In addition to pure interleaving semantics we can convert TAs to FSMTs having a parallelized interleaving behavior which allows parallelism of transitions causing no conflicts. This can dramatically reduce the number of steps during verification. Our experimental results show that our prototype implementation outperforms the stateoftheart model checkers UPPAAL and RED. 1
Satisfiability Modulo Software
, 2009
"... Formal verification is the act of proving correctness of a hardware or software system using formal methods of mathematics. In the last decade formal hardware verification has seen an increasing usage of Satisfiability Modulo Theories (SMT) solvers. SMT solvers check satisfiability of firstorder fo ..."
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Cited by 4 (0 self)
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Formal verification is the act of proving correctness of a hardware or software system using formal methods of mathematics. In the last decade formal hardware verification has seen an increasing usage of Satisfiability Modulo Theories (SMT) solvers. SMT solvers check satisfiability of firstorder formulas, where certain symbols are interpreted according to background theories like integer or bitvector arithmetic. Since the formulas used to encode correctness of hardware design are mostly quantifierfree, SMT solvers are built as theoryaware extensions of propositional satisfiability solvers. As a consequence, SMT solvers do not “naturally ” support quantified formulas, which are needed for verification of complex software systems. Thus, while SMT solvers are already an industrially viable tool for formal hardware verification, software applications are not as developed. This thesis focuses on both the software verification specific problems in the construction of SMT solvers, as well as SMTspecific parts of a software verification system. On the SMT side, we present algorithms for efficient