An alternative goal-oriented hierarchical representation of solid objects for computer integrated manufacturing

The face-to-face composition (FFC) graph is the formal representation of a family of models of solid objects for advanced engineering applications. It is a multirooted hierarchical structure based on boundary representation and is capable of accommodating different conceptual views of the same object or assembly. A node of the FFC graph describes a volumetric object component consisting of a single shell, while its arcs correspond to connection faces between pairs of single components. Operators are available both for modifying the object and for changing the representation. Node groups define a correct order of evaluation of the FFC graph which produces a valid solid object at each step. The model also includes a formal definition of the notion `feature-of´ as an open subgraph corresponding to constructs not necessarily realizable on their own, such as rivet holes with pads