Bi-gram based Query Expansion Technique for Amharic Information Retrieval System

Information retrieval system has been using to connect users of the information and information repository corpora. Even though the task of information retrieval systems is to retrieve relevant information, it is very difficult to find a perfect information retrieval system which is capable of retrieving relevant and only relevant documents as per user's query. The aim of this research is to increase precision of an Amharic information retrieval system while preserving the original recall. In order to achieve this bi-gram technique has been adopted for the query expansion. The main reason for performing query expansion is to provide relevant documents as per users' query that can satisfy their information need. Because users are not fully knowledgeable about the information domain area, they mostly formulate weak queries to retrieve documents. Thus, they end up frustrated with the results found from an information retrieval system. Amharic language has many meaning for a single word and also the word can be found in different form. These are some of the challenges that made the information retrieval system performing at very low level. Query expansion methods outperform in differentiating the various meanings of a polysemous term and find synonymous terms for reformulating users' query. Bi-gram technique uses the underling theory of expanding a query; using terms that appear adjacent to a query term frequently. The proposed technique was integrated to an information retrieval system. Then the retrieval system is tested with and without using bi-gram technique query expansion. The test result showed that bi-gram based method outperformed the original query based retrieval, and scored 8% improvement in total F-measure. This is an encouraging result to design an applicable search engine, for Amharic language.