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Chapter 10
Knowledge Sharing and Reuse

Asunción Gómez-Pérez


CONTENTS

1. Introduction
2. Problems with Reuse Software or Share Knowledge
3. What is an Ontology?
4. Ontologies and Knowledge Bases
5. Ontological Commitments
6. Types of Ontologies
7. How to Use Ontologies
8. Design Criteria
9. Ontology Development Process
9.1. Project Management Activities
9.2. Development-Oriented Activities
9.3. Integral Activities
10. Ontology Life Cycle
11. Methodology to Build Ontologies
11.1. Specification
11.2. Knowledge Acquisition
11.3. Conceptualization
11.3.1. Conceptualization of Concepts
    11.3.2. Conceptualization of Verbs
    11.3.3. Conceptualization of Rules and Formulas
11.4. Formalization
11.5. Integration
11.6. Implementation
11.7. Evaluation
11.8. Documentation
12. Interlinguas
12.1. KIF
12.2. PIF
13. The Most Well-Known Ontologies
13.1. Cyc
13.2. Example of a Knowledge Representation-Ontology: The Frame Ontology
13.3. Linguistic Ontologies
13.4. Engineering Ontologies
13.5. Planning Ontologies
14. Tools: Ontology Server
15. Systems That Use Ontologies
16. Conclusion
Acknowledgments
References

1. INTRODUCTION

In 1991, the ARPA Knowledge Sharing Effort (Neches et al., 1991) revolutionized the way in which intelligent systems were built. They proposed the following:

"Building knowledge-based systems today usually entails constructing new knowledge bases from scratch. It could instead be done by assembling reusable components. System developers would then only need to worry about creating the specialized knowledge and reasoners new to the specific task of their system. This new system would interoperate with existing systems, using them to perform some of its reasoning. In this way, declarative knowledge, problem-solving techniques and reasoning services would all be shared among systems. This approach would facilitate building bigger and better systems cheaply... ."

Since then, there have been workshops on ontologies in SSS-97 in Stanford, on ontological engineering; ECAI-96 in Budapest (August 1996), on the practical aspects of ontology development; IJCAI (August 1995), on basic ontological issues in knowledge sharing; La Jolla (November 1994); ECAI-94 in Amsterdam (August 1994) on implemented ontologies; IJCAI-93 in Chambery (August 1993), on knowledge sharing and information interchange; and the workshop on formal ontology in Padova, Italy (March 1993). Ideas from many papers included in the proceedings of recent conferences and ontologies workshops are collected here.

On examining the literature, it could be said that many ontologies have been developed by different groups, adopting different approaches and using different methods and techniques. However, few papers have been published about how to proceed, showing the practices, design criteria, activities, methodologies, and tools used to build ontologies. The implication is clear: the absence of standardized activities, life cycles, and systematic methodologies, as well as a set of well-defined design criteria, techniques, and tools make ontologies development a craft rather than an engineering activity. So, the art will become engineering when there is a definition and standardization of a life cycle that goes from requirements definition to maintenance of the finished product, as well as methodologies and techniques that drive development.

This chapter does not seek to transform the ontological art into engineering. It only presents a view of how the knowledge-sharing industry is evolving, its terminology, the infrastructure, technology, and methodologies that make it possible, its main developments, as well as the principal research issues and future trends. The chapter is organized into three main parts. The first part is an introduction to this field. The goal of the second part is to explain the activities that readers interested in building ontologies from scratch should perform and in which order, as well as the set of techniques to be used in each phase of the building process. Finally, the third part presents the most well-known ontologies and systems that use ontologies.


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