Ambiguity in natural language requirements is an inherent challenge. Ambiguity arises when the user does not participate in the system development. Ambiguity once incorporated seeps into later stages of system development. In traditional software development approaches ambiguity is addressed at the inspection phase, which is manual, labour intensive and costly activity. Researchers have proposed several methods, techniques, approaches, tools etc. for avoidance, detection, and removal of ambiguity once requirements are specified. However, all the approaches utilize time and effort and require manual intervention. To the best of our knowledge, there are very few studies present in literature that focus on reducing ambiguity during requirements elicitation. Traditional techniques are reactive and address ambiguity once requirements are specified. We propose that a pro-active approach is needed for addressing ambiguity early i.e., during elicitation. Doing so will result in unambiguous requirements that can lead to successful development.  The proposed approach uses gamification i.e., use of game elements to engage users and keep them interested while performing the task at hand i.e., elicitation of unambiguous requirement.  The approach is supported via Gamified tool Gamify4Req, which uses the game concepts of avatar, leaderboard and points and badges.  The validation of the tool is performed on two case studies selected from software market, and user involvement is measured with help of a questionnaire. The findings show that the gamified tool outperforms the existing methods used in the industry for reducing ambiguity in requirements both in terms of number of identified ambiguities and time spent on the task. Moreover, the tool ensures user involvement which is measured with help of user involvement survey. usage activity and survey of users.

Index Terms- Requirements elicitation, semantic ambiguity, ambiguity rules, gamification, game elements, PBL (points, badges, leaderboards), game rules, POS tags