The complexity of industrial systems is steadily increasing. To face this complexity, the different engineering disciplines are designing models. These models are complex as they reflect the complexity of systems under study. Therefore, they need to be structured. In this article we study structural constructs of modeling languages used in systems engineering. We introduce for that purpose a small domain specific language, the so-called S2ML for System Structure Modeling Language. We show that a large class of actual modeling languages can be (re)constructed by plugging their underlying mathematical framework into S2ML.