SelfSync: A Dynamic Round-Trip Engineering Environment. Model-Driven Engineering (MDE) advocates the generation of software applications from models, which are views on certain aspects of the software. In this paper, we focus on a particular setup which consists of a graphical data modeling view and a view on an object-oriented implementation, which can be either textual or graphical. A challenge that arizes in the context of MDE is the notion of Round-Trip Engineering (RTE), where elements from both views can be manipulated and thus need to be synchronized. We systematically identify four fundamental RTE scenarios. In this paper, we employ the framework of these scenarios for explaining SelfSync, our approach and tool for providing dynamic support for RTE. In SelfSync, the entities of the data modeling view and the corresponding implementation objects are one and the same. Additionally, we present a comparison with related work accompanied by an extensive discussion.