Fatemeh Serpush - Faculty of Computer and Information Technology Engineering, Qazvin Branch, Islamic Azad University, Qazvin, Iran
Mohammadreza Keyvanpour - Department of Computer Engineering Alzahra University, Tehran, Iran

A major problem in information retrieval is the difficulty to define the information needs of user and on the other hand, when user offers your query there is a vast amount of information to retrieval. Different methods , therefore, have been suggested for query expansion which concerned with reconfiguring of query by increasing efficiency and improving the criterion accuracy in the information retrieval system. Accordingly in this paper, in addition to propose a new coherent categorization for approaches, we proceed to detailed identify them, and proper functional criteria to evaluate each of these approaches are suggested.

information retrieval; query expansion; knowledge models; relevant feedback