Most systems for automatic design operate on a restricted set of geometries (macros) which are limited by predefine interrelations. In this paper we propose a new general approach for modeling constraints on the topology and geometry of the constituent components, using a new formulation called QSR or Qualitative Spatial Reasoning. QSR is based on the hypothesis that important changes occur at points of tangency, and we show how this information alone can be used to preserve positional and directional information, as well as shape attributes such as aspect ratio. The model allows for incremental refinement of the geometric aspects of design by specifying further constraints on the specific geometry of the interconnected parts and their sub-components. We show how this can be used to maintain a solution space, from which a specific instance is chosen and displayed to the user for visual verification of the incomplete design. The same instance also sewes as a template for interactive design detailing. Kaywords: Geometric modeling, computer-aideddesign, spatial reasoning.