In defense of types in knowledge-based CAAD

There are two basic approaches to representation of design knowledge in knowledge-based CAAD systems, the type-based approach which has a long tradition, and the more recent typeless approach. Proponents of the latter have offered a number of arguments against the type-based approach which are reviewed in the paper and found rather unconvincing. Work within both paradigms is also reviewed and problems encountered under both approaches discussed. The analysis concludes with a recommendation of preserving the notion of types but in a form that avoids rigidity, and with hints at how certain technical problems involved in such an approach can be solved or avoided.