الفهرس 
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Abstract
An ontology defines a common vocabulary for researchers who need to share information in a domain. It includes machine-interpretable definitions of basic concepts in the domain and relations among them.
The reasons of using the ontology can be summarized in the following points:
• To share common understanding of the structure of information
among people or software agents.
• To enable reuse of domain knowledge.
• To make domain assumptions explicit.
• To separate domain knowledge from the operational knowledge.
• To analyze domain knowledge.
Ontology can be used in the following application areas: Information retrieval procedure, knowledge representation/sharing, semantic digital libraries, software engineering, natural-language processing, multi-agent
ystems, information systems in general, ontology based reasoning, policy language specification and database design.
Originally, ontologies were stored in a text based formats such as RDF, RDFS and OWL; this representation had difficulties in applying search and retrieval operations over ontologies.
The current approaches rely on data bases as a reservoir for storing ontologies. These approaches are based on general schemas such as triples and specific schemas such as Jena, Kaon, Sesame, Protege, OntoStduio and Ontolingua. Consequently, there is no unified approach for storing ontologies that can be said to be abstract and application independent.
This thesis surveys the available approaches for storing ontologies in data bases in order to investigate the generalization, strength and weakness of each approach. Additionally, it proposes an abstract model for ontology bases that can enable onto1.ogies to be modeled in a conceptual representation which hides the details of how ontologies are stored.
Results indicates that there is no approach more superior than the othe The introduced proposed model shows the best results since it can suppa relation of degree N and on the other side it provides an approach th keeps a static schema with almost no change on its structure.
It can provide abstract and unified approach for storing ontologies. In th’ work, a specific language Ontology Storage Language (OSL) similar t Data Storage Language (DSL) in databases is introduced. In addition t the specifications of Ontology Definition Language (ODL) and Onto log View Language (OVL) were also proposed. Finally, an Ontology Storag Language (OSL) was provided that could be useful for designin ontology bases and Ontology Base Management System (OBMS).