IfcShell

Definition from ISO/CD 10303-42:1992 This type collects together, for reference when constructing more complex models, the subtypes which have the characteristics of a shell. A shell is a connected object of fixed dimensionality d = 0; 1; or 2, typically used to bound a region. The domain of a shell, if present, includes its bounds and 0 £ X < ¥ .

A shell of dimensionality 0 is represented by a graph consisting of a single vertex. The vertex shall not have any associated edges.
A shell of dimensionality 1 is represented by a connected graph of dimensionality 1.
A shell of dimensionality 2 is a topological entity constructed by joining faces along edges. Its domain, if present, is a connected, orientable 2-manifold with boundary, that is, a connected, oriented, finite, non-self-intersecting surface, which may be closed or open.

Definition from IAI: Shells of dimensionality 0 and 1 are not part of the current IFC release.

NOTE: Corresponding STEP type: shell. Please refer to ISO/IS 10303-42:1994, p. 127 for the final definition of the formal standard. Only the select items closed_shell (IfcClosedShell) and open_shell (IfcOpenShell) have been incorporated in the current IFC release.

HISTORY: New type in IFC Release 2x

EXPRESS specification:

TYPE IfcShell = SELECT

(	IfcClosedShell, IfcOpenShell);

END_TYPE;