The paper discusses proposed solutions for constraint-based modelling,
with special emphasis on constructive approaches. A new constructive
scheme is proposed that is based on a nonevaluated, constructive solid
model. The model definition language is presented and discussed, with
the general architecture of the system and the structure of the inter
nal model representation. The proposed approach supports the instantia
tion of predefined models, parametric geometric operations in 1D, 2D a
nd 3D, variable topologies, and operations with structural constraints
.