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Ontology describes a domain of classes. It is defined as a conceptual model of knowledge representation. The concepts of the domain (classes), their attributes, their properties and their relationships are well described by the Ontology model. It also explains the meanings of the terms applicable to the domain. Ontology is one of the key components of semantic web technology. The semantic web technologies like Ontology, RDF and Sparql are used in describing different words and their dependencies by modeling the textual data. Components of Ontology include:

 • Concepts are also known as Classes. It is a unit of knowledge, shared among identified group of persons for the concept’s domain. There exists relationship among concepts.

 • Instances are individuals of concepts. They represent specific elements attached to the domain ontology. Instances are the “thing” represented by a concept.

Information Extraction (IE) and Ontology are related with one another like: Ontology is used in information extraction as part of understanding process of the domain; on the other hand, IE is used to design and enrich Ontology [7]. Common vocabulary and shared understanding among different people are enabled by Ontology. The contextual representation of data semantics is well described by the Ontology [8]. The UML diagrams along with Ontology support the biologists by classifying the entities and interactions between proteins and genes [9]. The terms (vocabularies) and the concepts (classes) in the source Ontology are used in term matching, thereby used in tagging the text documents. Thus the Ontology and their specifications are used in the information extraction process.