Although parametric design (also known as 'associative geometry') has been available commercially for at least a decade, it is not used in the typical architect's office. It is expensive and requires high-end computers; a typical installation could approach $US100,000 for software and hardware placing it beyond the reach of most architects. Parametric design software has been developed principally for mechanical engineers, civil engineers, industrial designers and for the transport industry all of whom make good use of products that allow the 'whole' to be resolved into a large number of associated and adaptable parts.

[Figure 1] shows a set of two objects with their dimensioned relationships. This example can be referred to as an explicit design. Any of the dimensioned parameters can be changed, but only through a sequence of erasures and redrawing. A parametrically generated model can be 'updated' by identifying one or more of the parameters and changing their values. [Figure 2] is an example of a parametrically generated model and shows the difference in philosophy between explicit and associative geometry. [Figure 3] shows the topological effect of reconfiguring the parameters.