A method and apparatus programmatically define structure within a physical modeling environment. The system and corresponding method of modeling, provides a computationally based modeling environment in which a physical entity can be modeled parametrically and hierarchically, if desired. A physical component of the physical entity is identified. The physical component is defined by a structural physical parameter and a behavior. The definitions combine to form a model element with the structural physical parameter using structural variables, and behaviors, that can be defined functionally.