Description Graphs Research Articles

HermiT: An OWL 2 Reasoner

This system description paper introduces the OWL 2 reasoner HermiT. The reasoner is fully compliant with the OWL 2 Direct Semantics as standardised by the World Wide Web Consortium (W3C). HermiT is based on the hypertableau calculus, and it supports a wide range of standard and novel optimisations that improve the performance of reasoning on real-world ontologies. Apart from the standard OWL 2 reasoning task of entailment checking, HermiT supports several specialised reasoning services such as class and property classification, as well as a range of features outside the OWL 2 standard such as DL-safe rules, SPARQL queries, and description graphs. We discuss the system's architecture, and we present an overview of the techniques used to support the mentioned reasoning tasks. We further compare the performance of reasoning in HermiT with that of FaCT++ and Pellet--two other popular and widely used OWL 2 reasoners.

Representing ontologies using description logics, description graphs, and rules

Description logics (DLs) are a family of state-of-the-art knowledge representation languages, and their expressive power has been carefully crafted to provide useful knowledge modeling primitives while allowing for practically effective decision procedures for the basic reasoning problems. Recent experience with DLs, however, has shown that their expressivity is often insufficient to accurately describe structured objects—objects whose parts are interconnected in arbitrary, rather than tree-like ways. DL knowledge bases describing structured objects are therefore usually underconstrained, which precludes the entailment of certain consequences and causes performance problems during reasoning. To address this problem, we propose an extension of DL languages with description graphs—a knowledge modeling construct that can accurately describe objects with parts connected in arbitrary ways. Furthermore, to enable modeling the conditional aspects of structured objects, we also extend DLs with rules. We present an in-depth study of the computational properties of such a formalism. In particular, we first identify the sources of undecidability of the general, unrestricted formalism. Based on that analysis, we then investigate several restrictions of the general formalism that make reasoning decidable. We present practical evidence that such a logic can be used to model nontrivial structured objects. Finally, we present a practical decision procedure for our formalism, as well as tight complexity bounds.

Satisfiability and reasoning mechanism of terminological cycles in description logic % MathType!MTEF!2!1!+- % feaagaart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqipC0df9qqqrpepC0xbbL8F4rqqrpepeea0xe9Lq-lc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pf0Firpepe0de9vr0-vr % 0-vqpWqaaeaabiGaciaacaqabeaadaqaaqaaaOqaaerbn9MBVrxEWv % gid9MCZLMDHbacfiqcaaQaa8NDamrr1ngBPrwtHrhAXaqeguuDJXwA % KbstHrhAG8KBLbacgaGccqGFsectaaa!46C0! $$ v\mathcal{L} $$

The current research works and the existing problems of terminological cycles in description logics are analyzed in this paper. Referring to the works of Baader F and Nebel B, we aim in a new direction. Firstly, description logic $$ v\mathcal{L} $$ is defined, and the description graphs GT and GJ are redefined. A syntax condition for the satisfiability of membership relation is given. By using this syntax condition, we prove the following: The subsumption reasoning in $$ v\mathcal{L} $$ with respect to gfp-model, lfp-model and descriptive model is polynomial.

A Semantics and Complete Algorithm for Subsumption in the CLASSIC Description Logic

This paper analyzes the correctness of the subsumption algorithm used in CLASSIC, a description logic-based knowledge representation system that is being used in practical applications. In order to deal efficiently with individuals in CLASSIC descriptions, the developers have had to use an algorithm that is incomplete with respect to the standard, model-theoretic semantics for description logics. We provide a variant semantics for descriptions with respect to which the current implementation is complete, and which can be independently motivated. The soundness and completeness of the polynomial-time subsumption algorithm is established using description graphs, which are an abstracted version of the implementation structures used in CLASSIC, and are of independent interest.

A knowledge-based specification technique for protocol development

This paper proposes a knowledge-based specification technique (KST) for protocol development. This technique semi-automatically translates a protocol described in an informal description (natural languages or graphs) into one described in formal specifications (Estelle and SDL). The translation processes are supported by knowledge stored in the knowledge base. This paper discusses the concept, the specification control mechanism of KST and the rules and algorithms for production of FSM's which is the basis of Estelle and SDL.