The report discusses proposed solutions for constraint-based modelling, with special emphasis on constructive approaches. A new constructive scheme that overcomes a number of the present limitations is proposed. It is based on a non-evaluated, constructive model. The proposed approach supports instantiation of pre-defined models, parametric geometric operations in 1D, 2D, and 3D, variable topologies, and operations with structural constraints. The EBNF specification of the model definition language is presented and discussed through several exemples.