Spatial user interaction result from considering spatial attributes (localization, orientation.. .) of entities or spatial relations between them (distance, relative position.. .) to trigger system functions. Recently, more and more spatial interactive applications exist in daily life (parking radar in cars, automatic doors in supermarkets and building...). Such interfaces offer more natural and intuitive interactions due to their facility to use or downright their transparency. According to our literature review on spatial interaction works, we noticed that most of them focused on the desire to demonstrate the relevance of the interaction paradigm itself. Unfortunately, only few works were conducted to standardize necessary concepts for the spatial interface development such as specification languages, modeling or simulation tools. These letters facilitate designers work and contribute to the democratization of this kind of interaction. In this context, we present in this paper, a modeling language called SUIL (Spatial User Interaction Language) and a framework for modeling and simulating spatial interfaces called SIMSIT (Spatial Interfaces Modeling and SImulation Tool).