Rada and Attea Journal of Science, 2017, Vol. 58, No.4B, pp: 2222-2235 DOI: 10.24996/ ijs.2017.58.4B.25 _________________________________ *Email: hudarada2016@gmail.com 2222 Understanding the Role of Positive and Negative Relations for Community Detection Problem in Signed Networks: A New Perspective Huda M. Rada * , Bara’a A. Attea . Department of Computer Science, College of Science, University of Baghdad, Baghdad, Iraq. Abstract In real world, almost all networks come out with positive and negative types of relations. The sign could reflect like-dislike, agreement-disagreement, friendship- enmity, and attraction-discouragement. The contribution of this paper is to introduce prototype definitions for both nodes and communities of signed networks according to the distribution of positive and negative signs over the network's links. Two types of nodes (strong and weak) are introduced. Accordingly, three types of communities are declared, these are strong, weak, and irregular (or noisy). The formulated definitions provide us with a new understanding for the difficulty raised in community detection problem in signed networks. One of the recent state-of-the-art multi-objective detection models (modeled after Liu et al.) is adopted in this study as the optimization function for one of the well-known decomposition based multi- objective evolutionary algorithm (MOEA/D). In the experiments, different levels of complex synthetic networks are generated, characterized, and used as test-bed to explore and evaluate the performance of MOEA/D for solving community detection problem. The results reveal that the accuracy of the network partitioning solutions is increased while increasing the percentage of strong nodes and strong communities and vice versa while increasing percentage of weak nodes and weak and irregular communities. Keywords: Community detection; graph partitioning; signed relation; social network analysis. فهمت المؤشرة: منظور جديدعات لمشبكاة كشف المجتمشكمة في مبية والسمبيليجات اعلقا دور ال مصطفى رضا هدى،* عطية اء عمي بر لحاسوبوم ا عم قسم اق.معة بغداد، بغداد، العروم، جا ، كمية العم خلصه ال لشبكاتعظم ا مقيلم الحقيلعا في ا تأتيليجابيةت اعلقاواع من ال بان والسمبية ، يمكن أن تعكس هذة لشارة العجابثل عدم ا م- لعجاب ، ا والعداوة وف والصداقةختل أللحباط ، ا البصمة في هذ البحث هي باطاتلبة عمى ارتلسا ات الموجبة والشارل توزيع امؤشرة من خلت اللشبكات في المجتمعا العقد وا تحديد انواع ين من العقات . هناك نوع الشبك. وفقا لذلك) القوية والضعيفة( دات عرفت وهيث من المجتمع هناك ثل ( لشاذة القوية والضعيفة والنظامية الغير ا) . ارت في أثي لمصعوبة التيفاهيم جديدةلمصاغة وفرت لنا مريف ا لتعا ت المؤشرةلشبكان المجتمع في اشكمة الكشف ع م، و ألحاليينحثين البا حد اموديل ال في مجال المتعددة ت ISSN: 0067-2904