# 8.8.3.22 IfcHalfSpaceSolid

## 8.8.3.22.1 Semantic definition

A half space solid divides the domain into two by a base surface. Normally, the base surface is a plane and divides the infinitive space into two and indicates the side of the half-space by agreeing or disagreeing to the normal of the plane.

Figure 8.8.3.22.A illustrates the definition of the IfcHalfSpaceSolid within a given coordinate system. The base surface is given by an unbounded plane, the red boundary is shown for visualization purposes only.

For a valid half space solid the surface shall divide the domain into exactly two subsets. Also, within the domain the surface shall be manifold and all surface normals shall point into the same subset.

Informal Propositions:

1. The base surface shall divide the domain into exactly two subsets. If the half space solid is of subtype boxed half space (IfcBoxedHalfSpace), the domain in question is that of the attribute enclosure. In all other cases the domain is all of space and the base surface shall be unbounded.
2. The base surface shall be an unbounded surface (subtype of IfcElementarySurface).

## 8.8.3.22.4 Formal representation

ENTITY IfcHalfSpaceSolid
SUPERTYPE OF (ONEOF
(IfcBoxedHalfSpace
,IfcPolygonalBoundedHalfSpace))
SUBTYPE OF (IfcGeometricRepresentationItem);
BaseSurface : IfcSurface;
AgreementFlag : IfcBoolean;
DERIVE
Dim : IfcDimensionCount := 3;
END_ENTITY;