—In cloud computing, modeling can be used to specify service topologies. Following a model-driven approach provisioning can be automated resulting in a significant reduction of time and costs. Yet, a forward engineering approach is limited to initial setups. That is, changes introduced posterior to a generation are not addressed per se when a complete regeneration is to be avoided. For dealing with differential changes of infrastructure service models, a model-based round-trip engineering approach is proposed that combines the power of model-driven generation with runtime reflection. For this, a de facto runtime model is reverse-engineered and model differences are calculated and operated on for enforcing a de jure model. While showcasing how to evolve a forward engineering approach accordingly, a particular implication of this contribution is the possibility to facilitate migration of cloud infrastructure services.