IFC 4.3.x development

5.4.3.50 IfcRelSpaceBoundary1stLevel

Change log

5.4.3.50.1 Semantic definitions at the entity

The 1st level space boundary defines the physical or virtual delimiter of a space by the relationship IfcRelSpaceBoundary1stLevel to the surrounding elements. 1st level space boundaries are characterizeda by:

• 1st level space boundaries are the boundaries of a space defined by the surfaces of building elements bounding this space (physical space boundaries) or by virtual surfaces provided by an adjacent space with no dividing wall.
• 1st level space boundaries do not consider any change of material in the bounding building elements, or different spaces/zones behind a wall or slab (floor or ceiling).
• 1st level space boundaries are differentiated in two ways: virtual or physical and internal,external, or undefined (internal and external) e.g. for a wall that is partially inside and outside.
• 1st level space boundaries form a closed shell around the space (so long as the space is completely enclosed) and include overlapping boundaries representing openings (filled or not) in the building elements (see implementers agreement below).

1st level space boundaries define a space by its boundary surfaces without taking anything on the other side of the bounding elements into account.

NOTE  1st level space boundaries are used e.g. in quantity take-off and facility management as they describe the surfaces for finishes. They cannot be directly used for thermal analysis. However 1st level space boundaries can provide the input to preprocessors to thermal analysis software that take 1st level space boundaries and perform the necessary transformation into 2nd level space boundaries that are required for energy analysis.

HISTORY  New entity in IFC4.

Relationship Use Definitions

As shown in Figure 1, the attribute ParentBoundary with inverse InnerBoundaries is provided to link the space boundaries of doors, windows, and openings to the parent boundary, such as of a wall or slab.

NOTE  The space boundary of the parent is not cut by the inner boundary - both overlap.

Geometry Use Definitions

See the definition at the supertype IfcRelSpaceBoundary for guidance on using the connection geometry for first level space boundaries.

5.4.3.50.1 Attributes

#	Attribute	Type	Description
IfcRoot
1	GlobalId	IfcGloballyUniqueId	Assignment of a globally unique identifier within the entire software world.
2	OwnerHistory	OPTIONAL IfcOwnerHistory	Assignment of the information about the current ownership of that object, including owning actor, application, local identification and information captured about the recent changes of the object, > NOTE  only the last modification in stored - either as addition, deletion or modification. > IFC4 CHANGE  The attribute has been changed to be OPTIONAL.
3	Name	OPTIONAL IfcLabel	Optional name for use by the participating software systems or users. For some subtypes of IfcRoot the insertion of the Name attribute may be required. This would be enforced by a where rule.
4	Description	OPTIONAL IfcText	Optional description, provided for exchanging informative comments.
IfcRelationship
IfcRelConnects
IfcRelSpaceBoundary
5	RelatingSpace	IfcSpaceBoundarySelect	Reference to one spaces that is delimited by this boundary.
6	RelatedBuildingElement	IfcElement	Reference to ~~Building~~ Element, that defines the Space Boundaries. > IFC2x CHANGE  The data type has been changed from IfcBuildingElement to IfcElement with upward compatibility for file based exchange. > IFC4 CHANGE  The attribute has been changed to be mandatory.
7	ConnectionGeometry	OPTIONAL IfcConnectionGeometry	Physical representation of the space boundary. Provided as a **curve or** surface given within the LCS of the space. > IFC2x CHANGE  The data type has been changed from IfcConnectionSurfaceGeometry to IfcConnectionGeometry with upward compatibility for file based exchange.
8	PhysicalOrVirtualBoundary	IfcPhysicalOrVirtualEnum	Defines, whether the Space Boundary is physical (Physical) or virtual (Virtual).
9	InternalOrExternalBoundary	IfcInternalOrExternalEnum	Defines, whether the Space Boundary is internal (Internal), or external, i.e. adjacent to open space (that can be an partially enclosed space, such as terrace (External).
IfcRelSpaceBoundary1stLevel
10	ParentBoundary	OPTIONAL IfcRelSpaceBoundary1stLevel	Reference to the host, or parent, space boundary within which this inner boundary is defined.
	InnerBoundaries	SET [0:?] OF IfcRelSpaceBoundary1stLevel FOR ParentBoundary	Reference to the inner boundaries of the space boundary. Inner boundaries are defined by the space boundaries of openings, doors and windows.

5.4.3.50.2 Entity inheritance

5.4.3.50.3 Definitions applying to General Usage

5.4.3.50.3.1 Identity

5.4.3.50.3.2 Revision Control

5.4.3.50.4 Formal representations

ENTITY IfcRelSpaceBoundary1stLevel
 SUPERTYPE OF (ONEOF
	(IfcRelSpaceBoundary2ndLevel))
 SUBTYPE OF (IfcRelSpaceBoundary);
	ParentBoundary : OPTIONAL IfcRelSpaceBoundary1stLevel;
 INVERSE
	InnerBoundaries : SET [0:?] OF IfcRelSpaceBoundary1stLevel FOR ParentBoundary;
END_ENTITY;