\input zb-basic \input zb-ioport \iteman{io-port 06089220} \itemau{Taentzer, Gabriele; Mantz, Florian; Lamo, Yngve} \itemti{Co-transformation of graphs and type graphs with application to model co-evolution.} \itemso{Ehrig, Hartmut (ed.) et al., Graph transformations. 6th international conference, ICGT 2012, Bremen, Germany, September 24--29, 2012. Proceedings. Berlin: Springer (ISBN 978-3-642-33653-9/pbk). Lecture Notes in Computer Science 7562, 326-340 (2012).} \itemab Summary: Meta-modeling has become the key technology to define do-main-specific modeling languages in model-driven engineering. Since do-main-specific modeling languages often change quite frequently, concepts are needed for the coordinated evolution of their meta-models as well as of their models, and possibly other related artifacts. In this paper, we present a new approach to the co-transformation of graphs and type graphs and show how it can be applied to model co-evolution. This means that models are specified as graphs while model relations, especially type-instance relations, are defined by graph morphisms specifying type conformance of models to their meta-models. Hence, meta-model evolution and accompanying model migrations are formally defined by co-transformations of instance and type graphs. In our approach, we clarify the type conformance of co-transformations, the completeness of instance graph transformations wrt. their type graph modifications, and the reflection of type graph transformations by instance graph transformations. Finally, we discuss strategies for automatically deducing instance graph transformation rules from given type graph transformations. \itemrv{~} \itemcc{} \itemut{meta-model evolution; model migration; graph transformation} \itemli{doi:10.1007/978-3-642-33654-6\_22} \end