The development of today-s complex products requires advanced integrated environments and modeling languages for modeling and simulation. Equation-based object-oriented declarative (EOO) languages are emerging as the key approach to physical system modeling and simulation. The increased ease of use, the high abstraction and the expressivity of EOO languages are very attractive properties. However, these attractive properties come with the drawback that programming and modeling errors are often hard to find. In this paper we propose an integrated framework for run-time debugging of equation-based modeling languages. The framework integrates classical debugging techniques with special techniques for debugging EOO languages and is based on graph visualization and interaction. The debugging framework targets the Modelica language.