Parametric and feature-based CAD models can be considered to represent families of similar objects. In current modelling systems, however, the semantics of such families are unclear and ambiguous. We present the Declarative Family of Objects Model (DFOM), which enables to adequately specify and maintain family semantics. In this model, not only geometry, but also topology is specified declaratively, by means of constraints. A family of objects is modelled by a DFOM with multiple realisations. A member of the family is modelled by adding constraints, e.g. to set dimension variables, until a single realisation remains. The declarative approach guarantees that the realisation of a family member is also a realisation of the family. The realisation of a family member is found by solving first the geometric constraints, and then the topological constraints. From the geometric solution, a cellular model is constructed. Topological constraints indirectly specify which combinations of cellul...
Hilderick A. van der Meiden, Willem F. Bronsvoort