Spatial interactions have a great potential in ubiquitous environments. Physical objects, endowed with interconnected sensors, cooperate in a transparent manner to help users in their daily tasks. In our context, we qualify an interaction as spatial if it results from considering spatial attributes (location, orientation, speed.. .) of the user's body or of a given object used by her/him. According to our literature review, we found that despite their benefits (simplicity, concision, naturalness.. .), spatial interactions are not as widespread as other interaction models such as graphical or tactile ones. We think that this fact is due to the lack of software tools and frameworks that can make the design and development of spatial interaction easy and fast. In this paper, we propose a spatial interaction modeling language named SUIL (Spatial User Interaction Language) which represents the first step towards the development of such tools. CCS CONCEPTS • Human centered computing; • Human Computer Interaction; • Ubiquitous and mobile computing.;