Soundness Preserving Approximation for TBox Reasoning

The Semantic Web-ISWC 2008, 2008

We introduce the notion of the mixed DL and entailment-based (DLE) OWL reasoning, defining a framework inspired from the hybrid and homogeneous paradigms for integration of rules and ontologies. The idea is to combine the TBox inferencing capabilities of the DL algorithms and the scalability of the rule paradigm over large ABoxes. Towards this end, we define a framework that uses a DL reasoner to reason over the TBox of the ontology (hybrid-like) and a rule engine to apply a domain-specific version of ABoxrelated entailments (homogeneous-like) that are generated by TBox queries to the DL reasoner. The DLE framework enhances the entailment-based OWL reasoning paradigm in two directions. Firstly, it disengages the manipulation of the TBox semantics from any incomplete entailment-based approach, using the efficient DL algorithms. Secondly, it achieves faster application of the ABoxrelated entailments and efficient memory usage, comparing it to the conventional entailment-based approaches, due to the low complexity and the domainspecific nature of the entailments.

2007

Abstract Tableau algorithms are currently the most widely used and empirically the fastest algorithms for reasoning in expressive description logics, including the important description logics and. Achieving a high level of performance on terminological reasoning in expressive description logics when using tableau-based algorithms requires the incorporation of a wide variety of optimizations. The description logic system FaCT++ implements a wide variety of such optimizations, some present in other reasoners and some novel or refined in FaCT++.

Lecture Notes in Computer Science, 2012

In order to support the vision of the Semantic Web, ontology reasoning needs to be highly scalable and efficient. A natural way to achieve scalability and efficiency is to develop parallel ABox reasoning algorithms for tractable OWL 2 profiles to distribute the load between different computation units within a reasoning system. So far there have been some work on parallel ABox reasoning algorithms for the pD* fragment of OWL 2 RL. However, there is still no work on parallel ABox reasoning algorithm for OWL 2 EL, which is the language for many influential ontologies (such as the SNOMED CT ontology). In this paper, we extend a parallel TBox reasoning algorithm [5] for ELHR+ to parallel ABox reasoning algorithms for ELH ⊥,R+ , which also supports the bottom concept so as to model disjointness and inconsistency. In design of algorithms, we exploit the characteristic of ABox reasonings to improve parallelisation and reduce unnecessary resource cost. Our evaluation shows that a naive implementation of our approach can compute all ABox entailments of a Not-Galen − ontology with about 1 million individuals and 9 million axioms in about 3 minutes.

Studia Logica

Description logics are a family of knowledge representation formalisms that are descended from semantic networks and frames via the system KL-ONE. During the last decade, it has been shown that the important reasoning problems (like subsumption and satisfiability) in a great variety of description logics can be decided using tableau-like algorithms. This is not very surprising since description logics have turned out to be closely related to propositional modal logics and logics of programs (such as propositional dynamic logic), for which tableau procedures have been quite successful. Nevertheless, due to different underlying intuitions and applications, most description logics differ significantly from run-of-the-mill modal and program logics. Consequently, the research on tableau algorithms in description logics led to new techniques and results, which are, however, also of interest for modal logicians. In this article, we will focus on three features that play an important rôle in description logics (number restrictions, terminological axioms, and role constructors), and show how they can be taken into account by tableau algorithms.

arXiv (Cornell University), 2018

We present a KE-tableau-based implementation of a reasoner for a decidable fragment of (stratified) set theory expressing the description logic DL 4LQS R,× (D) (DL 4,× D , for short). Our application solves the main TBox and ABox reasoning problems for DL 4,× D. In particular, it solves the consistency problem for DL 4,× D-knowledge bases represented in set-theoretic terms, and a generalization of the Conjunctive Query Answering problem in which conjunctive queries with variables of three sorts are admitted. The reasoner, which extends and optimizes a previous prototype for the consistency checking of DL 4,× D-knowledge bases (see [7]), is implemented in C++. It supports DL 4,× D-knowledge bases serialized in the OWL/XML format, and it admits also rules expressed in SWRL (Semantic Web Rule Language).

2009

Abstract We present a novel reasoning calculus for the description logic SHOIQ+—a knowledge representation formalism with applications in areas such as the Semantic Web. Unnecessary nondeterminism and the construction of large models are two primary sources of inefficiency in the tableau-based reasoning calculi used in state-of-the-art reasoners. In order to reduce nondeterminism, we base our calculus on hypertableau and hyperresolution calculi, which we extend with a blocking condition to ensure termination.

2018

We present a KE-tableau-based implementation of a reasoner for a decidable fragment of (stratified) set theory expressing the description logic DL〈4LQSR,×〉(D) (DL D , for short). Our application solves the main TBox and ABox reasoning problems for DL D . In particular, it solves the consistency problem for DL D -knowledge bases represented in set-theoretic terms, and a generalization of the Conjunctive Query Answering problem in which conjunctive queries with variables of three sorts are admitted. The reasoner, which extends and optimizes a previous prototype for the consistency checking of DL D -knowledge bases (see [7]), is implemented in C++. It supports DL D -knowledge bases serialized in the OWL/XML format, and it admits also rules expressed in SWRL (Semantic Web Rule Language).

Abstract. HermiT is a reasoner for the Description Logic SHOIQ+. The system is based on a novel “hypertableau” calculus and includes a number of new optimizations. HermiT demonstrates significantly faster performance when classifying large and complex ontologies than other state-of-the-art reasoners. HermiT is also the first reasoner able to classify a number of important knowledge bases, including the original version of the GALEN ontology.

Integrated Computer-Aided Engineering, 2008

Reasoning in a Knowledge Base (KB) is one of the most important applications of Description Logic (DL) reasoners. The execution time and storage space requirements are both significant factors that directly influence the performance of a reasoning algorithm. In this paper, we investigate a new technique for optimizing DL reasoning in order to minimize the above two factors as much as possible. This technique is applied to speed up TBox and ABox reasoning, especially for large TBoxes. The incorporation of this technique with previous optimization techniques in current DL systems can effectively solve intractable inferences. Our technique is called "overlap ontology decomposition", in which the decomposition of a given ontology into many sub-ontologies is implemented such that the semantics and inference services of the original ontology are preserved. We are concerned about how to reason effectively with multiple KBs and how to improve the efficiency of reasoning over component ontologies.

2010

State of the art reasoners for expressive description logics, such as those that underpin the OWL ontology language, are typically based on highly optimized implementations of (hyper) tableau algorithms. Despite numerous optimizations, certain ontologies encountered in practice still pose significant challenges to such reasoners, mainly because of the size of the model abstractions that they construct.