Study On The Theory And Practice Of Ontology And Ontology-based Agricultural Document Retrieval System--Floricultural Ontology Modeling

Ontology originated in philosophy. Aristotle defined "Ontology" as science about "being" in the world. Since 1990s, ontology has been introduced in Artificial Intelligence, Knowledge Engineering and Library & Information sciences. And then the definition of ontology has been changed. Ontology learning includes the research on knowledge representation and knowledge organization in the domains mentioned above. In Library & Information science, ontology is a vocabulary with the specification of relationships between terms about a special domain. Ontology learning and practicing have been developing rapidly these years. The theory and technology of ontology get maturer than before. The applying of ontology gets more extensive than before. The research level of ontology in China is not as developed as the western countries now. There is still no domain-oriented tentative or demo system based on ontology in Library & Information fields in China.The ontological theory and method have been described systematically on the basis of intensive investigation of large number of documents and web pages on ontology learning in this dissertation. The origin, definition, type and role of ontology have been described. The state of arts of ontology research in China and foreign countries has been introduced. The distinctions between ontology and thesaurus, ontology and semantic network have been analyzed. The comparisons have been made among 5 famous ontology-based knowledge systems, 7 methods of building ontology, 15 ontology specification languages, 5 tools for editing ontology and 3 paradigms of applying ontology in some scientific fields. A FOM (Floricultural ontology model) has been firstly built in China in order to validate the possibility of constructing ontology-based knowledge organization. A FORS (Floricultural document tentative ontology-based Retrieval System) has been firstly developed in China in order to validate the reusability of FOM.FORS was based on Chinese Agricultural Scientific & Technological Document Database. FOM offered a knowledge base to FORS. OpenCyc's upper ontology and inference engine were used in constructing FORS. Oracle 9i was used as the DBMS of FORS, and Oracle designer was used as the toolkit for developing the document-querying and knowledge-importing interfaces! The validation showed that FORS had already possessed some functions of reasoning query, removing the divergent "understanding" mislead by literal Chinese words looked same like each other, giving "true" or "false" about the simple questions. The advantages of ontology-based system have been shown somewhat by FORS. The approaches in building domain ontology or even ontology-based system have also shown in this dissertation.The dissertation concluded as follows:1) Cyc KB and OntoSeek are ontology-based systems which are maturer than others.2) "Seven-step" method and "METHONTOLOGY" are the maturer methods of building ontologies. There are still no standard for building ontology up to now.3) Loom, CycL and OWL are ontology specification languages which are perfecter than others, though they have some shortcomings: Loom is not easy to learn and use, CycL is not used widely since it's not based on XML, and OWL's all functions needs to be excavated since it is a recently recommended standard.4) Ontology editing tools based on 4GL (such as Java) can't satisfy the actual needs of building ontologies, and they do not provide a right logic hierarchy梐 right upper ontology.5) Domain ontology can't be built and used independently. Domain ontology must be based on an upper ontology system with correct logic structure. And the inference engine of upper ontology system must be reused in domain ontology system.6) The number of concepts in Cyc ?KB > the number of concepts in Agricultural ontology > the number of concepts of Horticulture > the numbers of core concepts in Floricultural ontology. The structure of number distribution of concept among general ontology, upper domain ontology and domain ontology li...