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RACER system description
, 2001
"... Abstract. RACER implements a TBox and ABox reasoner for the logic SHIQ. RACER was the first fullfledged ABox description logic system for a very expressive logic and is based on optimized sound and complete algorithms. RACER also implements a decision procedure for modal logic satisfiability proble ..."
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Cited by 452 (41 self)
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Abstract. RACER implements a TBox and ABox reasoner for the logic SHIQ. RACER was the first fullfledged ABox description logic system for a very expressive logic and is based on optimized sound and complete algorithms. RACER also implements a decision procedure for modal logic satisfiability problems (possibly with global axioms). 1
Using an Expressive Description Logic: FaCT or Fiction?
 In Proc. of KR98
, 1998
"... Description Logics form a family of formalisms closely related to semantic networks but with the distinguishing characteristic that the semantics of the concept description language is formally defined, so that the subsumption relationship between two concept descriptions can be computed by a suitab ..."
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Cited by 273 (50 self)
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Description Logics form a family of formalisms closely related to semantic networks but with the distinguishing characteristic that the semantics of the concept description language is formally defined, so that the subsumption relationship between two concept descriptions can be computed by a suitable algorithm. Description Logics have proved useful in a range of applications but their wider acceptance has been hindered by their limited expressiveness and the intractability of their subsumption algorithms. This paper addresses both these issues by describing a sound and complete tableaux subsumption testing algorithm for a relatively expressive Description Logic which, in spite of the logic's worst case complexity, has been shown to perform well in realistic applications. 1 INTRODUCTION Description Logics (DLs) form a family of formalisms which have grown out of knowledge representation techniques using frames and semantic networks
Practical reasoning for very expressive description logics
 Journal of the Interest Group in Pure and Applied Logics 8
, 2000
"... Description Logics (DLs) are a family of knowledge representation formalisms mainly characterised by constructors to build complex concepts and roles from atomic ones. Expressive role constructors are important in many applications, but can be computationally problematical. We present an algorithm t ..."
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Cited by 185 (22 self)
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Description Logics (DLs) are a family of knowledge representation formalisms mainly characterised by constructors to build complex concepts and roles from atomic ones. Expressive role constructors are important in many applications, but can be computationally problematical. We present an algorithm that decides satisfiability of the DL ALC extended with transitive and inverse roles and functional restrictions with respect to general concept inclusion axioms and role hierarchies; early experiments indicate that this algorithm is wellsuited for implementation. Additionally, we show that ALC extended with just transitive and inverse roles is still in PSpace. We investigate the limits of decidability for this family of DLs, showing that relaxing the constraints placed on the kinds of roles used in number restrictions leads to the undecidability of all inference problems. Finally, we describe a number of optimisation techniques that are crucial in obtaining implementations of the decision procedures, which, despite the hight worstcase complexity of the problem, exhibit good performance with reallife problems. 1
The FaCT system
 In Proceedings of the International Conference on Automated Reasoning with Analytic Tableaux and Related Methods (TABLEAUX’98), volume 1397 in Lecture Notes in Artificial Intelligence
, 1998
"... Abstract. FaCT is a Description Logic classifier which has been implemented as a testbed for a highly optimised tableaux satisfiability (subsumption) testing algorithm. The correspondence between modal and description logics also allows FaCT to be used as a theorem prover for the propositional moda ..."
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Cited by 151 (15 self)
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Abstract. FaCT is a Description Logic classifier which has been implemented as a testbed for a highly optimised tableaux satisfiability (subsumption) testing algorithm. The correspondence between modal and description logics also allows FaCT to be used as a theorem prover for the propositional modal logics K, KT, K4 and S4. Empirical tests have demonstrated the effectiveness of the optimised implementation and, in particular, of the dependency directed backtracking optimisation. 1
A Proposal for a Description Logic Interface
"... Most description logic (DL) systems present the application programmer with a functional interface, often defined using a Lisplike syntax. Such interfaces may be more or less complex, depending on the sophistication of the implemented system, and may be more or less compliant with the KRSS descript ..."
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Cited by 143 (18 self)
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Most description logic (DL) systems present the application programmer with a functional interface, often defined using a Lisplike syntax. Such interfaces may be more or less complex, depending on the sophistication of the implemented system, and may be more or less compliant with the KRSS description logic specification [7]. The Lisp style of the KRSS syntax reflects the fact that Lisp is still the most common implementation language for DLs. This can create considerable barriers to the use of DL systems by application developers, who often prefer other languages (in particular the currently ubiquitous Java), and who are becoming more accustomed to component based software development environments. In such an environment, a DL might naturally be viewed as a self contained component, the details of whose implementation, and even the precise location in which its code is being executed, is hidden from the application [2]. This approach has several advantages: the issue of implementation language is finessed; the API can be defined in some standard formalism intended for the purpose; a mechanism
High Performance Reasoning with Very Large Knowledge Bases: A Practical Case Study
, 2000
"... We present an empirical analysis of optimization ..."
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A Comparison of Reasoning Techniques for Querying Large Description Logic ABoxes
, 2006
"... Abstract. Many modern applications of description logics (DLs) require answering queries over large data quantities, structured according to relatively simple ontologies. For such applications, we conjectured that reusing ideas of deductive databases might improve scalability of DL systems. Hence, i ..."
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Cited by 68 (10 self)
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Abstract. Many modern applications of description logics (DLs) require answering queries over large data quantities, structured according to relatively simple ontologies. For such applications, we conjectured that reusing ideas of deductive databases might improve scalability of DL systems. Hence, in our previous work, we developed an algorithm for reducing a DL knowledge base to a disjunctive datalog program. To test our conjecture, we implemented our algorithm in a new DL reasoner KAON2, which we describe in this paper. Furthermore, we created a comprehensive test suite and used it to conduct a performance evaluation. Our results show that, on knowledge bases with large ABoxes but with simple TBoxes, our technique indeed shows good performance; in contrast, on knowledge bases with large and complex TBoxes, existing techniques still perform better. This allowed us to gain important insights into strengths and weaknesses of both approaches. 1
Optimising Description Logic Subsumption
 Journal of Logic and Computation
, 1999
"... Effective optimisation techniques can make a dramatic difference in the performance of knowledge representation systems based on expressive description logics. With currentlyavailable desktop computers, systems that incorporate these techniques can effectively reason in description logics with intr ..."
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Cited by 57 (16 self)
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Effective optimisation techniques can make a dramatic difference in the performance of knowledge representation systems based on expressive description logics. With currentlyavailable desktop computers, systems that incorporate these techniques can effectively reason in description logics with intractable inference. Because of the correspondence between description logics and propositional modal logic, difficult problems in propositional modal logic can be effectively solved using the same techniques.
DLP System Description
 Collected Papers from the International Description Logics Workshop (DL'98
, 1998
"... DLP (Description Logic Prover) is an experimental description logic knowledge representation system. DLP currently implements a superset of propositional dynamic logic as well as K (m) and KT (m) . Although DLP is an experimental system, it nonetheless provides a fast satisfiability checker for ..."
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Cited by 50 (9 self)
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DLP (Description Logic Prover) is an experimental description logic knowledge representation system. DLP currently implements a superset of propositional dynamic logic as well as K (m) and KT (m) . Although DLP is an experimental system, it nonetheless provides a fast satisfiability checker for the above propositional modal logics as well as a fast reasonder for knowledge bases.
Reasoning with Axioms: Theory and Practice
 IN PROC. OF THE 7TH INT. CONF. ON PRINCIPLES OF KNOWLEDGE REPRESENTATION AND REASONING (KR 2000
, 2000
"... When reasoning in description, modal or temporal logics it is often useful to consider axioms representing universal truths in the domain of discourse. Reasoning with respect to an arbitrary set of axioms is hard, even for relatively inexpressive logics, and it is essential to deal with such a ..."
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Cited by 47 (17 self)
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When reasoning in description, modal or temporal logics it is often useful to consider axioms representing universal truths in the domain of discourse. Reasoning with respect to an arbitrary set of axioms is hard, even for relatively inexpressive logics, and it is essential to deal with such axioms in an ecient manner if implemented systems are to be effective in real applications. This is particularly relevant to Description Logics, where subsumption reasoning with respect to a terminology is a fundamental problem. Two optimisation techniques that have proved to be particularly eective in dealing with terminologies are lazy unfolding and absorption. In this paper we seek to improve our theoretical understanding of these important techniques. We define a formal framework that allows the techniques to be precisely described, establish conditions under which they can be safely applied, and prove that, provided these conditions are respected, subsumption testing algo...