This volume constitutes the proceedings of the 4th International United Information Systems Conference, UNISCON 2012, which was held in Yalta, Ukraine, during June 1-3, 2012. UNISCON 2012 was affiliated with the 8th International Conference on ICT in Education, Research, and Industrial Applications, ICTERI 2012. The 14 full papers, four short papers, and three extended abstracts presented with a keynote speech were carefully reviewed and selected from 96 submissions. The topical sections covered are: data management; applications; modeling and semantics; and social issues in information systems.