Model interpreters play an essential role in model-integrated systems: they transform domain-specific models into executable models. The state-ot-the-art of model interpreter writing needs to be advanced to enhance the reusability and maintainability of this software. This paper presents an approach which makes this possible through the use of structured specifications. These specifications let the programmer express traversal strategies and visitation actions in very high-level terms. From these specifications efficient traversal code can be automatically generated.