System engineers spend a signi cant part of their time debugging the systems they develop, i.e., nding and xing the cause of failures initially observed using veri cation and validation techniques such as testing, model checking, and simulation. While veri cation and validation techniques are nding their way into model-driven engineering processes and tools, locating the source of a failure (a defect) in a modelled system is still mostly a manual task. Although program debugging techniques are well-established, only a few debugging techniques and tools for models have been proposed, which are most often implemented in an ad-hoc way. Implementing such tools is complicated due to the wide variety of models and modelling languages used throughout system development. In this context, the International Workshop on Debugging in Model-Driven Engineering (MDEbug) aims to bring together researchers and members of the industry to discuss the wide range of exciting problems and challenges related to the debugging of models. The second edition of this workshop was a full-day event at the ACM/IEEE 21st International Conference on Model Driven Engineering Languages and Systems (MODELS) on October 16th, 2018 in Copenhagen, Denmark. This year, we speci cally encouraged submissions that focused on the notion of \stepping", as this concept has proven a crucial element for implementing debugging techniques: the goal was to investigate the relation of stepping to formalism semantics and debugging operations. After a thorough review process, four contributions were accepted to be presented at the workshop. Three contributions focus on providing debugging support for di erent formalisms: model transformations (and their contracts), software agents, and metamodels, while the fourth contribution proposes a vocabulary for classifying stepping operations across formalisms. The workshop's program was divided into a morning session, consisting of a keynote by Peter Gorm Larssen on the Vienna Development Method (VDM) and the presentations of the accepted papers, and an afternoon session, which consisted of a plenary discussion. We thank the MODELS 2018 organization for providing the opportunity to organize this workshop, especially general chair Andrzej Wasowski (IT University of Copenhagen, Denmark) and workshop chairs Regina Hebig and Thorsten Berger (University of Gothenburg-Chalmers, Sweden). We also thank everyone that has submitted a paper, the participants of the workshops, and the presenters of the accepted papers. We thank Peter Gorm Larsen for his inspiring keynote; together with the presented papers, this has lead to an interesting and active discussion session with the participants. Our thanks also go to members of the Program Committee, for their accurate reviews and for their help in choosing relevant papers to the workshop and helping them improve before publication.
Mauricio Alferez Shaukat Ali Reda Bendraou Arnaud Blouin Andrei Chi Federico Ciccozzi Benoit Combemale Jonathan Corley Andrea D'Ambrogio Julien Deantoni Davide Di Ruscio Juergen Dingel Martin Gogolla Je Gray Robert Heinrich Nicolas Hili Levi Lucio Tanja Mayerhofer Tim Molderez Eugene Syriani Jeremie Tatibouet Matthias Tichy Massimo Tisi Javier Troya Antonio Vallecillo