ABSTRACT
Boolean operations are especially useful when the modelling process can be thought of in terms of sculpting solid objects by means of addition, subtraction, and intersection. Groups of CAD objects can be composed of elements from different layers, and layers can in turn include blocks taken from different layers. The phenomenon of layering has a precursor in traditional drawing practice, but the use of grouping does not. Concepts such as grouping are computational ideas that affect the way designers design.
