Even the more complex structures of the tower and hall can be created using automated procedures. For example, the tower requires a relatively small number of parameters to be defined (its overall height, XYZ co-ordinates of its base, the height of the various floors and the roof, etc.) and these can be used in conjunction with boolean algebra on a set of box primitives and 3D lines and faces to generate the overall structure. Only the relationships between the structural elements are defined in advance (providing the 'glue' that holds the building components together) – the user parameters define all other aspects of the structure. Hence changes in the basic parameters will change the appearance of the tower, but not its overall form – however, changes in the structural relationships will define a different form of tower altogether.