Parametric models are typically built from various geometric or non-geometric entities, e.g. a projection curve depends on the curve that is going to be projected and the surface it is supposed to lay on. In most programs the user creates the desired object first (in this case the projection curve) - and is subsequently asked to supply the necessary objects (surface, curve and possible projection direction) until the configuration is complete. In CAESES/FFW missing information is indicated by a * next to the required attribute and you can set the relationship via drag and drop or typing. However, if you have selected a surface and a curve already when creating the projection curve, they will be automatically associated to the attributes. Note: Whenever the selection set fits to a creator called, the attributes will be set immediately. For every object you will find a list of available creators in the type documentation.