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354
The DLV System for Knowledge Representation and Reasoning
 ACM Transactions on Computational Logic
, 2002
"... Disjunctive Logic Programming (DLP) is an advanced formalism for knowledge representation and reasoning, which is very expressive in a precise mathematical sense: it allows to express every property of finite structures that is decidable in the complexity class ΣP 2 (NPNP). Thus, under widely believ ..."
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Cited by 455 (100 self)
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Disjunctive Logic Programming (DLP) is an advanced formalism for knowledge representation and reasoning, which is very expressive in a precise mathematical sense: it allows to express every property of finite structures that is decidable in the complexity class ΣP 2 (NPNP). Thus, under widely believed assumptions, DLP is strictly more expressive than normal (disjunctionfree) logic programming, whose expressiveness is limited to properties decidable in NP. Importantly, apart from enlarging the class of applications which can be encoded in the language, disjunction often allows for representing problems of lower complexity in a simpler and more natural fashion. This paper presents the DLV system, which is widely considered the stateoftheart implementation of disjunctive logic programming, and addresses several aspects. As for problem solving, we provide a formal definition of its kernel language, functionfree disjunctive logic programs (also known as disjunctive datalog), extended by weak constraints, which are a powerful tool to express optimization problems. We then illustrate the usage of DLV as a tool for knowledge representation and reasoning, describing a new declarative programming methodology which allows one to encode complex problems (up to ∆P 3complete problems) in a declarative fashion. On the foundational side, we provide a detailed analysis of the computational complexity of the language of
A Novel Combination of Answer Set Programming with Description Logics for the Semantic Web
 IN PROC. KR2004
, 2004
"... Abstract. We present a novel combination of disjunctive logic programs under the answer set semantics with description logics for the Semantic Web. The combination is based on a wellbalanced interface between disjunctive logic programs and description logics, which guarantees the decidability of th ..."
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Cited by 282 (59 self)
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Abstract. We present a novel combination of disjunctive logic programs under the answer set semantics with description logics for the Semantic Web. The combination is based on a wellbalanced interface between disjunctive logic programs and description logics, which guarantees the decidability of the resulting formalism without assuming syntactic restrictions. We show that the new formalism has very nice semantic properties. In particular, it faithfully extends both disjunctive programs and description logics. Furthermore, we describe algorithms for reasoning in the new formalism, and we give a precise picture of its computational complexity. We also provide a special case with polynomial data complexity. 1
Preferred Answer Sets for Extended Logic Programs
 ARTIFICIAL INTELLIGENCE
, 1998
"... In this paper, we address the issue of how Gelfond and Lifschitz's answer set semantics for extended logic programs can be suitably modified to handle prioritized programs. In such programs an ordering on the program rules is used to express preferences. We show how this ordering can be used ..."
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Cited by 157 (20 self)
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In this paper, we address the issue of how Gelfond and Lifschitz's answer set semantics for extended logic programs can be suitably modified to handle prioritized programs. In such programs an ordering on the program rules is used to express preferences. We show how this ordering can be used to define preferred answer sets and thus to increase the set of consequences of a program. We define a strong and a weak notion of preferred answer sets. The first takes preferences more seriously, while the second guarantees the existence of a preferred answer set for programs possessing at least one answer set. Adding priorities
A general Datalogbased framework for tractable query answering over ontologies
 In Proc. PODS2009. ACM
, 2009
"... Ontologies play a key role in the Semantic Web [4], data modeling, and information integration [16]. Recent trends in ontological reasoning have shifted from decidability issues to tractability ones, as e.g. reflected by the work on the DLLite family of tractable description logics (DLs) [11, 19]. ..."
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Cited by 134 (23 self)
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Ontologies play a key role in the Semantic Web [4], data modeling, and information integration [16]. Recent trends in ontological reasoning have shifted from decidability issues to tractability ones, as e.g. reflected by the work on the DLLite family of tractable description logics (DLs) [11, 19]. An important result of these works is that the main
MinimalChange Integrity Maintenance Using Tuple Deletions
, 2008
"... We address the problem of minimalchange integrity maintenance in the context of integrity constraints in relational databases. We assume that integrityrestoration actions are limited to tuple deletions. We identify two basic computational issues: repair checking (is a database instance a repair of ..."
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Cited by 127 (10 self)
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We address the problem of minimalchange integrity maintenance in the context of integrity constraints in relational databases. We assume that integrityrestoration actions are limited to tuple deletions. We identify two basic computational issues: repair checking (is a database instance a repair of a given database?) and consistent query answers [ABC99] (is a tuple an answer to a given query in every repair of a given database?). We study the computational complexity of both problems, delineating the boundary between the tractable and the intractable. We consider denial constraints, general functional and inclusion dependencies, as well as key and foreign key constraints. Our results shed light on the computational feasibility of minimalchange integrity maintenance. The tractable cases should lead to practical implementations. The intractability results highlight the inherent limitations of any integrity enforcement mechanism, e.g., triggers or referential constraint actions, as a way of performing minimalchange integrity maintenance.
Data Complexity of Reasoning in Very Expressive Description Logics
 IN PROC. IJCAI 2005
, 2005
"... Data complexity of reasoning in description logics (DLs) estimates the performance of reasoning algorithms measured in the size of the ABox only. We show that, even for the very expressive DL SHIQ, satisfiability checking is data complete for NP. For applications with large ABoxes, this can be a mor ..."
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Cited by 127 (23 self)
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Data complexity of reasoning in description logics (DLs) estimates the performance of reasoning algorithms measured in the size of the ABox only. We show that, even for the very expressive DL SHIQ, satisfiability checking is data complete for NP. For applications with large ABoxes, this can be a more accurate estimate than the usually considered combined complexity, which is EXPTIMEcomplete. Furthermore, we identify an expressive fragment, HornSHIQ, which is data complete for P, thus being very appealing for practical usage.
Backdoors to typical case complexity
, 2003
"... There has been significant recent progress in reasoning and constraint processing methods. In areas such as planning and finite modelchecking, current solution techniques can handle combinatorial problems with up to a million variables and five million constraints. The good scaling behavior of thes ..."
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Cited by 122 (14 self)
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There has been significant recent progress in reasoning and constraint processing methods. In areas such as planning and finite modelchecking, current solution techniques can handle combinatorial problems with up to a million variables and five million constraints. The good scaling behavior of these methods appears to defy what one would expect based on a worstcase complexity analysis. In order to bridge this gap between theory and practice, we propose a new framework for studying the complexity of these techniques on practical problem instances. In particular, our approach incorporates general structural properties observed in practical problem instances into the formal complexity
Mulval: A logicbased network security analyzer
 In 14th USENIX Security Symposium
, 2005
"... To determine the security impact software vulnerabilities have on a particular network, one must consider interactions among multiple network elements. For a vulnerability analysis tool to be useful in practice, two features are crucial. First, the model used in the analysis must be able to automati ..."
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Cited by 100 (19 self)
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To determine the security impact software vulnerabilities have on a particular network, one must consider interactions among multiple network elements. For a vulnerability analysis tool to be useful in practice, two features are crucial. First, the model used in the analysis must be able to automatically integrate formal vulnerability specifications from the bugreporting community. Second, the analysis must be able to scale to networks with thousands of machines. We show how to achieve these two goals by presenting MulVAL, an endtoend framework and reasoning system that conducts multihost, multistage vulnerability analysis on a network. MulVAL adopts Datalog as the modeling language for the elements in the analysis (bug specification, configuration description, reasoning rules, operatingsystem permission and privilege model, etc.). We easily leverage existing vulnerabilitydatabase and scanning tools by expressing their output in Datalog and feeding it to our MulVAL reasoning engine. Once the information is collected, the analysis can be performed in seconds for networks with thousands of machines. We implemented our framework on the Red Hat Linux platform. Our framework can reason about 84 % of the Red Hat bugs reported in OVAL, a formal vulnerability definition language. We tested our tool on a real network with hundreds of users. The tool detected a policy violation caused by software vulnerabilities and the system administrators took remediation measures. 1
A uniform integration of higherorder reasoning and external evaluations in answerset programming
 In Proceedings of the 19th International Joint Conference on Artificial Intelligence (IJCAI05
, 2005
"... We introduce HEX programs, which are nonmonotonic logic programs admitting higherorder atoms as well as external atoms, and we extend the wellknown answerset semantics to this class of programs. Higherorder features are widely acknowledged as useful for performing metareasoning, among other task ..."
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Cited by 99 (42 self)
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We introduce HEX programs, which are nonmonotonic logic programs admitting higherorder atoms as well as external atoms, and we extend the wellknown answerset semantics to this class of programs. Higherorder features are widely acknowledged as useful for performing metareasoning, among other tasks. Furthermore, the possibility to exchange knowledge with external sources in a fully declarative framework such as AnswerSet Programming (ASP) is nowadays important, in particular in view of applications in the Semantic Web area. Through external atoms, HEX programs can model some important extensions to ASP, and are a useful KR tool for expressing various applications. Finally, complexity and implementation issues for a preliminary prototype are discussed. 1