ISO 10303-521:2003 specifies the interpretation of the integrated resources to satisfy the requirement for the definition of a shape representation containing open shells defined as connected face sub sets. The domain of each connected face sub set is part of the domain of another open, or closed shell. Within the connected face sub set individual faces or edges may be identified as being subfaces, or subedges.
The following are within the scope of ISO 10303-521:2003:
- 3D geometry;
- advanced faces;
- connected face sub sets;
- mappings and geometric transformations;
- open shells;
- relationships between domains of topological objects;
- unbounded geometry with associated topological boundaries;
- use of topology to bound geometric entities.
The following are outside the scope of ISO 10303-521:2003:
- 2D geometry other than for the definition of a pcurve in the parameter space of a surface;
- boundary representation solid models;
- bounded curves other than polylines and B-spline curves;
- bounded surfaces other than B-spline surfaces;
- non-manifold geometry;
- offset curves and surfaces;
- unbounded geometry without topological boundaries.