Teferi, Dereje(Dr)Janfa, Welde2018-11-112023-11-182018-11-112023-11-182014-10-05http://etd.aau.edu.et/handle/12345678/14151The availability of a plenty of information and knowledge sources has demanded a large amount of effort in the development and enhancement of Information Retrieval techniques. Query expansion has been one of the important techniques in an information retrieval area in order to increase the efficiency and effectiveness of the search engine. Query expansion, improves the performance of the IR system by augmenting additional word to the user query from the given knowledge source. Adding additional power full words to the user query helps to generate more useful information to the user. This research focuses on automatic query expansion mechanism to increase the searching power of the user query. Many types of query expansion have been applied and tested to facilitate the information retrieval process. In this research work, an attempt is made to integrate an ontology based query expansion technique to enhance the effectiveness of the system in retrieval process. Ontologies are usually huge repositories of concepts and relations between concepts in a certain domain. Using the ontologies in information retrieval improves the retrieval goal. The aim of this research is to explore the impact of the use of ontology for query expansion to improve retrieval results. Small size domain specific corpus dependent ontology is constructed and used in the proposed query expansion model. Experiments are carried out on the system before and after integrating the proposed techniques. The results show that ontology based query expansion has resulted in a higher number of relevant documents being retrieved compared to other query expansion process. Overall, ontology based query expansion improves recall by 42% and system performance by 7%. The major challenge is constructing domain specific ontology and corpus that is an important element in this research which needs more work in the future.enOntology Based Query ExpansionThesis