Showing papers by "Ian Horrocks published in 2004"
01 Jan 2004
TL;DR: This document contains a structured informal description of the full set of {owL} language constructs and is meant to serve as a reference for {OWL} users who want to construct {OWl} ontologies.
Abstract: The {W}eb {O}ntology {L}anguage {OWL} is a semantic markup language for publishing and sharing ontologies on the {W}orld {W}ide {W}eb. {OWL} is developed as a vocabulary extension of {RDF} (the {R}esource {D}escription {F}ramework) and is derived from the {DAML}+{OIL} {W}eb {O}ntology {L}anguage. {T}his document contains a structured informal description of the full set of {OWL} language constructs and is meant to serve as a reference for {OWL} users who want to construct {OWL} ontologies.
2,508 citations
TL;DR: It is shown how to reduce ontology entailment for the OWL DL and OWL Lite ontology languages to knowledge base satisfiability in (respectively) the SHOIN(D) and SHIF( D) description logics.
520 citations
TL;DR: This paper describes the design and implementation of a service matchmaking prototype that uses a DAML -S based ontology and a description logic reasoner to compare ontology-based service descriptions to represent the semantics of service descriptions.
Abstract: The semantic Web can make e-commerce interactions more flexible and automated by standardizing ontologies, message content, and message protocols. This paper investigates how semantic and Web Services technologies can be used to support service advertisement and discovery in e-commerce. In particular, it describes the design and implementation of a service matchmaking prototype that uses a DAML -S based ontology and a description logic reasoner to compare ontology-based service descriptions. By representing the semantics of service descriptions, the matchmaker enables the behavior of an intelligent agent to approach more closely that of a human user trying to locate suitable Web services. The performance of this prototype implementation was tested in a realistic agent-based e-commerce scenario.
442 citations
17 May 2004
TL;DR: The expressive power of ORL is discussed, showing that the ontology consistency problem is undecidable, and how reasoning support for ORL might be provided are discussed.
Abstract: Although the OWLWeb Ontology Language adds considerable expressive power to the Semantic Web it does have expressive limitations, particularly with respect to what can be said about properties. Wepresent ORL (OWL Rules Language), a Horn clause rules extension to OWL that overcomes many of these limitations. ORL extends OWL in a syntactically and semantically coherent manner: the basic syntax for ORL rules is an extension of the abstract syntax for OWL DL and OWLLite; ORL rules are given formal meaning via an extension of the OWLDL model-theoretic semantics; ORL rules are given an XML syntax basedon the OWL XML presentation syntax; and a mapping from ORL rules to RDF graphs is given based on the OWL RDF/XML exchange syntax. Wediscuss the expressive power of ORL, showing that the ontology consistency problem is undecidable, provide several examples of ORLusage, and discuss how reasoning support for ORL might be provided.
359 citations
TL;DR: The OWL query language (OWL-QL) is presented as a candidate standard language and protocol for query-answering dialogues among Semantic Web computational agents using knowledge represented in the W3Cs ontology web language ( OWL).
325 citations
TL;DR: A tableau algorithm is presented for this DL extended with role inclusion axioms (RIAs) of the form Ro S ⊆ P and its implementation is reported on, which behaves well in practise and provides important additional functionality in a medical terminology application.
183 citations
Proceedings Article•
01 Jan 2004
TL;DR: An application aimed at solving some of the scalability problems that arise when reasoning with the large numbers of individuals envisaged in the semantic web, which scales to sizes where all other existing applications fail.
Abstract: We present an application – the Instance Store – aimed at solving some of the scalability problems that arise when reasoning with the large numbers of individuals envisaged in the semantic web. The approach uses well-known techniques for reducing description logic reasoning with individuals to reasoning with concepts. Crucial to the implementation is the combination of a description logic terminological reasoner with a traditional relational database. The resulting form of inference, although specialised, is sound and complete and sufficient for several interesting applications. Most importantly, the application scales to sizes (over 100,000s individuals) where all other existing applications fail. This claim is substantiated by a detailed empirical evaluation of the Instance Store in contrast with existing alternative approaches.
140 citations
07 Nov 2004
TL;DR: This paper reports on some experiments designed to explore the feasibility of using existing general-purpose FOL provers to reason with OWL DL, and extends the approach to SWRL, a proposed rule language extension to OWL.
Abstract: OWL DL corresponds to a Description Logic (DL) that is a fragment of classical first-order predicate logic (FOL) Therefore, the standard methods of automated reasoning for full FOL can potentially be used instead of dedicated DL reasoners to solve OWL DL reasoning tasks In this paper we report on some experiments designed to explore the feasibility of using existing general-purpose FOL provers to reason with OWL DL We also extend our approach to SWRL, a proposed rule language extension to OWL
84 citations
Journal Article•
TL;DR: This work shows how a tableaux algorithm for SHIQ can be extended to support role boxes that include range and domain axioms, and proves that the extended algorithm is still a decision procedure for the satisfiability and subsumption of SHIQ concepts w.r.t. such a role box.
Abstract: We show how a tableaux algorithm for SHIQ can be extended to support role boxes that include range and domain axioms, prove that the extended algorithm is still a decision procedure for the satisfiability and subsumption of SHIQ concepts w.r.t. such a role box, and show how support for range and domian axioms can be exploited in order to add a new form of absorption optimisation called role absorption. We illustrate the effectiveness of the optimised algorithm by analysing the perfomance of our FaCT++ implementation when classifying terminologies derived from realistic ontologies.
76 citations
Posted Content•
TL;DR: In this paper, the authors propose a new intermediate knowledge representation (KR) contained within this intersection: Description Logic Programs (DLP) and the closely related Description Horn Logic (DHL) which is an expressive fragment of first-order logic (FOL).
Abstract: We show how to interoperate, semantically and inferentially, between the leading Semantic Web approaches to rules (RuleML Logic Programs) and ontologies (OWL/DAML+OIL Description Logic) via analyzing their expressive intersection. To do so, we define a new intermediate knowledge representation (KR) contained within this intersection: Description Logic Programs (DLP), and the closely related Description Horn Logic (DHL) which is an expressive fragment of first-order logic (FOL). DLP provides a significant degree of expressiveness, substantially greater than the RDF-Schema fragment of Description Logic. We show how to perform DLP-fusion: the bidirectional translation of premises and inferences (including typical kinds of queries) from the DLP fragment of DL to LP, and vice versa from the DLP fragment of LP to DL. In particular, this translation enables one to "build rules on top of ontologies": it enables the rule KR to have access to DL ontological definitions for vocabulary primitives (e.g., predicates and individual constants) used by the rules. Conversely, the DLP-fusion technique likewise enables one to "build ontologies on top of rules": it enables ontological definitions to be supplemented by rules, or imported into DL from rules. It also enables available efficient LP inferencing algorithms/implementations to be exploited for reasoning over large-scale DL ontolo
Proceedings Article•
01 Oct 2004
TL;DR: This talk will give a brief history of DLs and of DL applications, in particular their application in the context of the Semantic Web, and an overview of the reasoning techniques that are employed by state of the art DL implementations, and which enable them to be effective in realistic applications in spite of the high worst case complexity of their basic inference problems.
Abstract: Description Logics (DLs) are a family of logic based Knowledge Representation formalisms descended from semantic networks and KL-ONE. They are distinguished by having formal (model theoretic) semantics, and by the provision of (sound and complete) inference services, with several highly optimised implementations now being available. DLs have a wide range of applications, but are perhaps best know as ontology languages (they provide the basis for recent "Semantic Web" ontology languages such as OIL, DAML+OIL and OWL). In this talk I will give a brief history of DLs and of DL applications, in particular their application in the context of the Semantic Web. If time permits, I will then give an overview of the reasoning techniques that are employed by state of the art DL implementations, and which enable them to be effective in realistic applications, in spite of the high worst case complexity of their basic inference problems. Finally, I will point out some interesting areas for future research, in particular those related to the Semantic Web application area.
TL;DR: The OWL Query Language (OWL-QL) as discussed by the authors is a standard language and protocol for query-answering dialogues among Semantic Web computational agents using knowledge represented in the OWL.
Abstract: This paper discusses the issues involved in designing a query language for the Semantic Web and presents the OWL Query Language (OWL-QL) as a candidate standard language and protocol for query-answering dialogues among Semantic Web computational agents using knowledge represented in the W3C's Ontology Web Language (OWL). OWL-QL is a formal language and precisely specifies the semantic relationships among a query, a query answer, and the knowledge base(s) used to produce the answer. Unlike standard database and Web query languages, OWL-QL supports query-answering dialogues in which the answering agent may use automated reasoning methods to derive answers to queries, as well as dialogues in which the knowledge to be used in answering a query may be in multiple knowledge bases on the Semantic Web, and/or where those knowledge bases are not specified by the querying agent. In this setting, the set of answers to a query may be of unpredictable size and may require an unpredictable amount of time to compute.
01 Jan 2004
TL;DR: This deliverable shows examples about approximating symbolic inference engines in a Semantic Web environment and approaches of language weakening, knowledge compilation, and approximated deduction.
Abstract: This deliverable shows examples about approximating symbolic inference engines in a Semantic Web environment. Approaches of language weakening, knowledge compilation, and approximated deduction are presented. The last one is evaluated in practical applications with mixed results.
Journal Article•
TL;DR: Why it is necessary to extend the existing datatypes approaches to the datatype group approach, in order to meet the above new requirements for DL reasoning services is explained.
Abstract: The OWL [2] datatype formalism (or simply OWL datatyping) presents some new requirements for DL reasoning services, in terms of semantics (to allow the use of so-called 'un-supported' datatypes), expressive power (to support enumerated datatypes) and datatype construction mechanism (both datatypes and datatype expressions). On the other hand, OWL datatyping is expected to be extended to include more expressive power. E.g., OWL datatyping does not provide a general framework for user-defined datatypes, such as XML Schema derived datatypes, nor does it support n-ary datatype predicates (such as the binary predicate > for integers), not to mention user-defined datatype predicates (such as the binary predicate > for non-negative integers). In this poster, we explain why it is necessary to extend the existing datatype approaches to the datatype group approach, in order to meet the above new requirements. It was Baader and Hanschke [1] who first presented a rigorous treatment of datatype predicates (or simply predicates). In their approach, a concrete domain [1, 4] is composed of a set of datatype values (such as integers) and a set of n-ary predicates (such as '<') defined over these values with obvious (fixed) extensions. Horrocks and Sattler [3] proposed the so called 'type system approach', which can be seen as a simplified version of the concrete domain approach, where the datatype domain (of a datatype interpretation) is regarded as a universal concrete domain and datatypes are treated as unary predicates in the universal concrete domain. In short, in the above two approaches, datatypes are nothing but unary predicates. In OWL datatyping, however, people take another view. A Datatype d distinguishes from a predicate in that it is characterised not only by the value spaces V (d), but also a lexical space, L(d), which is a set of Unicode strings, and a total mapping L2V (d) from the lexical space to the value space. E.g., boolean is a datatype with value space {true, f alse}, lexical space {T,F,1,0} and lexical-to-value mapping {T → true, F → f alse, 1 → true, 0 → f alse}. Data values can be represented by typed literals or plain literals, where typed literals are combinations of string and datatype URIs, while plain literals are simply strings, with optional language tag. E.g., \" 1 \" ˆˆxsd:boolean is a typed literal, while \" 1 \" is a plain literal. Therefore, when we extend OWL datatyp-ing to support predicates, we should not …
01 Jan 2004
TL;DR: A unified framework in which the existing (and future) proposals of integrating different sorts of rule based language with the OWL DL Web ontology language can be compared and in particular interested in the axiom-based approach.
Abstract: EU-IST Network of Excellence (NoE) IST-2004-507482 KWEB Deliverable D2.5.1 (WP2.5) We provide a unified framework in which the existing (and future) proposals of integrating different sorts of rule based language with the OWL DL Web ontology language can be compared. We are in particular interested in the axiom-based approach, as the SWRL proposal is a special case of it. We identify serval decidable sub-languages of SWRL with their complexity results and further explore several (including datatype predicate, fuzzy and context) extensions of SWRL. Keyword list: description logics, ontology language, rule language, query language