How ontologies provide the semantics, as explained here with the help of Harry Potter and his owl Hedwig.

/pdf/ontologies-and-the-semantic-web-16ku0ruzae.pdf

Ontologies and the semantic web

A review of wireless sensors and networks' applications in agriculture

This introduction presents the main motivations for the development of Description Logics (DLs) as a formalism for representing knowledge, as well as some important basic notions underlying all systems that have been created in the DL tradition. In addition, we provide the reader with an overview of the entire book and some guidelines for reading it.We first address the relationship between Description Logics and earlier semantic network and frame systems, which represent the original heritage of the field. We delve into some of the key problems encountered with the older efforts. Subsequently, we introduce the basic features of DL languages and related reasoning techniques.DL languages are then viewed as the core of knowledge representation systems. considering both the structure of a DL knowledge base and its associated reasoning services. The development of some implemented knowledge representation systems based on Description Logics and the first applications built with such systems are then reviewed.Finally, we address the relationship of Description Logics to other fields of Computer Science. We also discuss some extensions of the basic representation language machinery; these include features proposed for incorporation in the formalism that originally arose in implemented systems, and features proposed to cope with the needs of certain application domains.

/pdf/an-introduction-to-description-logic-52mep6mrpy.pdf

An Introduction to Description Logic

Description logics (DLs) and rules are formalisms that emphasize different aspects of knowledge representation: whereas DLs are focused on specifying and reasoning about conceptual knowledge, rules are focused on nonmonotonic inference. Many applications, however, require features of both DLs and rules. Developing a formalism that integrates DLs and rules would be a natural outcome of a large body of research in knowledge representation and reasoning of the last two decades; however, achieving this goal is very challenging and the approaches proposed thus far have not fully reached it. In this paper, we present a hybrid formalism of MKNFpknowledge bases, which integrates DLs and rules in a coherent semantic framework. Achieving seamless integration is nontrivial, since DLs use an open-world assumption, while the rules are based on a closed-world assumption. We overcome this discrepancy by basing the semantics of our formalism on the logic of minimal knowledge and negation as failure (MKNF) by Lifschitz. We present several algorithms for reasoning with MKNFp knowledge bases, each suitable to different kinds of rules, and establish tight complexity bounds.

https://www.cs.ox.ac.uk/people/boris.motik/pubs/mr10mknf-rules.pdf

Reconciling description logics and rules

Publisher Summary This chapter discusses description logics (DLs), which are a family of logic-based knowledge representation languages that can be used to represent the terminological knowledge of an application domain in a structured and formally well-structured way. It discusses their provenience and history and explains the way the field has developed. It describes the basic DL ALC in some detail, including definitions of syntax, semantics, and basic reasoning services, and discusses important extensions such as inverse roles, number restrictions, and concrete domains. It discusses (1) the relationship between DLs and other formalisms, in particular first order and modal logics, (2) the most commonly used reasoning techniques, in particular tableau, resolution, and automata based techniques, and (3) the computational complexity of basic reasoning problems. After reviewing some of the most prominent applications of DLs, in particular ontology language applications, the chapter discusses other aspects of DL research.

/pdf/chapter-3-description-logics-4ljbqj5har.pdf

Chapter 3 Description Logics

Existing classification schemes and thesauri are lacking in well-defined semantics and structural consistency. Empowering end users in searching collections of ever increasing magnitudes with performance far exceeding plain free-text searching (as used in many Web search engines), and developing systems that not only find but also process information for action, requires far more powerful and complex knowledge organization systems (KOSs). The paper presents a conceptual structure and transition procedure to support the shift from a traditional KOS towards a full-fledged and semantically rich KOS. The proposed structure also complies with other interoperability approaches like RDFS and XML in the Web environment. AGROVOC, a traditional thesaurus developed and maintained by the Food and Agriculture Organization (FAO) of the United Nations, serves as a case study for exploring the reengineering of a traditional thesaurus into a fully-fledged ontology. We start the process of developing an inventory of specific relationship types with well-defined semantics for the agricultural domain and explore the rules-as-you-go approach to streamlining the reengineering process.

Reengineering Thesauri for New Applications: the AGROVOC Example

This paper illustrates the conversion from a traditional thesaurus in agriculture (AGROVOC) to a new system, the Agricultural Ontology Service Concept Server (AOS/CS). The Concept Server will serve as a multilingual repository of concepts in the agricultural domain providing
ontological relationships and a rich, semantically sound terminology. The Food and
Agriculture Organization recently developed the underlying model for this new system in the Web ontology language OWL. In this paper, we describe the purpose of this conversion and the use of OWL and highlight in particular the core features of the developed OWL model.
We go on to explain how it evolves and differs from the traditional thesaurus approach.

From AGROVOC to the Agricultural Ontology Service / Concept Server - An OWL Model for Creating Ontologies in the Agricultural Domain.

SUMMARY The semantic heterogeneity of Web information in the Agricultural domain presents tremendous information retrieval challenges. This article presents work taking place at the Food and Agriculture Organizations (FAO) that addresses this challenge. Based on the analysis of resources in the domain of agriculture, this paper proposes (a) an application profile (AP) for dealing with the problem of heterogeneity originating from differences in terminologies, domain coverage, and domain modelling, and (b) a root application ontology (AAO) based on the application profile which can serve as a basis for extending knowledge of the domain. The paper explains how even a small investment in the enhancement of relationships among vocabularies, both metadata and domain-specific, yield a relatively large return on investment.

/pdf/towards-an-infrastructure-for-semantic-applications-4uiqx3qk1z.pdf

Anita C. Liang

Papers

Reengineering Thesauri for New Applications: the AGROVOC Example

From AGROVOC to the Agricultural Ontology Service / Concept Server - An OWL Model for Creating Ontologies in the Agricultural Domain.

Towards an Infrastructure for Semantic Applications: Methodologies for Semantic Integration of Heterogeneous Resources