Lars Bendix, Pär Emanuelsson:
Requirements for Practical Model Merge - an Industrial Perspective, pdf
in Proceedings of the 12th International Conference on Model Driven Engineering Languages and Systems - MODELS '09, Denver, Colorado, October 4-9, 2009.

Abstract:
All the usual support tools that developers are used to must be in place, if the use of model-centric development in companies has to take off. Industry deals with big models and many people working on the same model. Collaboration in a team inevitably leads to parallel work creating different versions that eventually will have to be merged together. However, our experience is that at present the support for model merge is far from optimal. In this paper, we put forward a number of requirements to practical merge tools, based on our analysis of literature, merge tool evaluations, interviews with developers, and a number of use cases for concurrent development of models. We found future work to do for both tool vendors and academic research. Fortunately we also uncovered a few tips and tricks that companies using model-centric development can implement on the short term while waiting for better times.