Abstract
Web 2.0 transformed the way people express their opinions about different entities. The web is indeed huge source of user generated contents. Number of online reviews available on the Web is increasing day by day which forces user to read most of them to get decision oriented information. Opinion mining address this problem by analyzing, summarizing and presenting opinions expressed in online reviews. Different opinion mining systems have been proposed and discussed in the literature. In this paper, authors present a comparison of state of the art opinion mining systems. The objectives of this work are to discuss significant state of the art opining mining systems and their comparison based on different design considerations using various metrics.