IfcOpeningElement

Semantic definitions at the entity

Entity definition

The opening element stands for opening, recess or chase, all reflecting voids. It represents a void within any element that has physical manifestation. Openings must be handled by all sectors and disciplines in AEC/FM industry, therefore the interoperability for opening elements is provided at this high level.

There are two different types of opening elements:

an opening, where the thickness of the opening is greater or equal to the thickness of the element;
a recess or niche, where the thickness of the recess is smaller than the thickness of the element.

The inherited attribute ObjectType should be used to capture the differences,

the attribute is set to 'Opening' for an opening or
the attribute is set to 'Recess' for a recess or niche.
If the value for ObjectType is omitted, opening is assumed.

An IfcOpeningElement has to be inserted into a building element (all subtypes of IfcBuildingElement) by using the IfcRelVoidsElement relationship. ~~It is also directly linked to the spatial structure of the project (and here normally to the IfcBuildingStorey) by using the IfcRelContainedInSpatialStructure relationship~~. It should not be linked directly to the spatial structure of the project, i.e. the inverse relationship ContainedInStructure shall be NIL. It is assigned to the spatial structure through the elements it penetrates.

HISTORY New entity in IFC Release 1.0

IFC2x PLATFORM CHANGE: The intermediate ABSTRACT supertypes IfcFeatureElement and IfcFeatureSubtraction have been added between IfcElement and IfcOpeningElement with upward compatibility.

Property Set Use Definition:

The property sets relating to the IfcOpeningElement are defined by the IfcPropertySet and attached by the IfcRelDefinesByProperties relationship. It is accessible by the inverse IsDefinedBy relationship. The following property set definitions specific to the IfcOpeningElement are part of this IFC release:

Pset_OpeningElementCommon: common property set for all opening occurrences

Quantity Use Definition:

The quantities relating to the IfcOpeningElement are defined by the IfcElementQuantity and attached by the IfcRelDefinesByProperties. The following quantities are foreseen, but will be subjected to the local standard of measurement:

Name	Description	Value Type
NominalArea	Area of the opening as viewed by an elevation view (for wall openings) or as viewed by a ground floor view (for floor openings). The exact definition and calculation rules depend on the method of measurement used.	IfcQuantityArea
NominalVolume	Volume of the opening. The exact definition and calculation rules depend on the method of measurement used.	IfcQuantityVolume

Geometry Use Definitions

The geometric representation of IfcOpeningElement is given by the IfcProductDefinitionShape and IfcLocalPlacement allowing multiple geometric representations.

Local Placement

The local placement for IfcOpeningElement is defined in its supertype IfcProduct. It is defined by the IfcLocalPlacement, which defines the local coordinate system that is referenced by all geometric representations.

The PlacementRelTo relationship of IfcLocalPlacement should point to the local placement of the same element, which is voided by the opening, i.e. referred to by VoidsElement.RelatingBuildingElement.

Geometric Representation

Currently, the use of 'SweptSolid', 'Brep', and 'MappedRepresentation' representation is supported.

Swept Solid Representation with Horizontal Extrusion
The 'SweptSolid' geometric representation of IfcOpeningElement, using horizontal extrusion direction (for walls), is defined using the swept area solid geometry. The following attribute values for the IfcShapeRepresentation holding this geometric representation shall be used:

RepresentationIdentifier : 'Body'
RepresentationType : 'SweptSolid'

The following additional constraints apply to the swept solid representation:

Solid: IfcExtrudedAreaSolid is required, the set of IfcShapeRepresentation.Items may include a single, or multiple, instances of IfcExtrudedAreaSolid.
Profile: IfcRectangleProfileDef, IfcCircleProfileDef and IfcArbitraryClosedProfileDef shall be supported.
Extrusion: The profile shall be extruded horizontally (i.e. perpendicular to the extrusion direction of the voided element), e.g. for wall openings, or vertically (i.e. in the extrusion direction of the voided element), e.g., for floor openings. If multiple instances of IfcExtrudedAreaSolid are used, the extrusion direction should be equal.

Special agreement for defining openings in round building elements, e.g., in round walls. The opening width, in case of a rectangular opening equal with the IfcRectangleProfileDef.XDim, is defined as the straight line distance between two parallel jambs. If the jambs are defined radial (to the center of the arc used to define the round wall) then the opening width is defined to be the outer arc length.

NOTE: In case of non-parallel jambs, the shape representation shall be a 'SweptSolid' representation with vertical extrusion.

EXAMPLE for openings

The following interpretation of dimension parameter applies for rectangular openings:

IfcRectangleProfileDef.YDim interpreted as opening width
IfcRectangleProfileDef.XDim interpreted as opening height

NOTE: Rectangles are now defined centric, the placement location has to be set:

IfcCartesianPoint(XDim/2,YDim/2)

EXAMPLE for recesses

The following interpretation of dimension parameter applies for rectangular recess:

IfcRectangleProfileDef.YDim interpreted as recess width
IfcRectangleProfileDef.XDim interpreted as recess height
IfcExtrudedAreaSolid.Depth is interpreted as recess depth

NOTE: Rectangles are now defined centric, the placement location has to be set:

IfcCartesianPoint(XDim/2,YDim/2)

NOTE: The local placement directions for the IfcOpeningElement are only given as an example, other directions are valid as well.

NOTE In case of recesses also profiles of type IfcArbitraryProfileDefWithVoid shall be supported as a 'SweptSolid' representation.

Swept Solid Representation with Vertical Extrusion
The 'SweptSolid' geometric representation of IfcOpeningElement, using vertical extrusion direction (for walls), is defined using the swept area solid geometry, however the extrusion direction may be vertical, i.e. in case of a wall opening, the extrusion would be in the direction of the wall height. The following attribute values for the IfcShapeRepresentation holding this geometric representation shall be used:

RepresentationIdentifier : 'Body'
RepresentationType : 'SweptSolid'

The following additional constraints apply to the swept solid representation:

Solid: IfcExtrudedAreaSolid is required, the set of IfcShapeRepresentation.Items may include a single, or multiple, instances of IfcExtrudedAreaSolid.
Profile: IfcRectangleProfileDef, IfcCircleProfileDef and IfcArbitraryClosedProfileDef shall be supported.
Extrusion: The profile shall be extruded vertically, i.e. for wall openings along the extrusion direction of the voided element. If multiple instances of IfcExtrudedAreaSolid are used, the extrusion direction should be equal.

Vertical extrusions shall be used when an opening or recess has a non rectangular foot print geometry that does not change along the height of the opening or recess.

Brep Representation
The general b-rep geometric representation of IfcOpeningElement is defined using the Brep geometry. The Brep representation allows for the representation of complex element shape. The following attribute values for the IfcShapeRepresentation holding this geometric representation shall be used:

RepresentationIdentifier : 'Body'
RepresentationType : 'Brep'

Attribute definitions

#	Attribute	Type	Cardinality	Description	A

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	A
IfcRoot
1	GlobalId	IfcGloballyUniqueId	[1:1]	Assignment of a globally unique identifier within the entire software world.	X
2	OwnerHistory	IfcOwnerHistory	[1:1]	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.	X
3	Name	IfcLabel	[0:1]	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.	X
4	Description	IfcText	[0:1]	Optional description, provided for exchanging informative comments.	X
IfcObjectDefinition
	IsDecomposedBy	IfcRelDecomposes @RelatingObject	S[0:?]	Reference to the decomposition relationship, that allows this object to be the composition of other objects. An object can be decomposed by several other objects.	X
	Decomposes	IfcRelDecomposes @RelatedObjects	S[0:1]	References to the decomposition relationship, that allows this object to be a part of the decomposition. An object can only be part of a single decomposition (to allow hierarchical strutures only).	X
	HasAssociations	IfcRelAssociates @RelatedObjects	S[0:?]	Reference to the relationship objects, that associates external references or other resource definitions to the object.. Examples are the association to library, documentation or classification.	X
IfcObject
5	ObjectType	IfcLabel	[0:1]	The type denotes a particular type that indicates the object further. The use has to be established at the level of instantiable subtypes. In particular it holds the user defined type, if the enumeration of the attribute PredefinedType is set to USERDEFINED.	X
	IsDefinedBy	IfcRelDefines @RelatedObjects	S[0:?]	Set of relationships to type or property (statically or dynamically defined) information that further define the object. In case of type information, the associated IfcTypeObject contains the specific information (or type, or style), that is common to all instances of IfcObject referring to the same type.	X
IfcProduct
6	ObjectPlacement	IfcObjectPlacement	[0:1]	Placement of the product in space, the placement can either be absolute (relative to the world coordinate system), relative (relative to the object placement of another product), or constraint (e.g. relative to grid axes). It is determined by the various subtypes of IfcObjectPlacement, which includes the axis placement information to determine the transformation for the object coordinate system.	X
7	Representation	IfcProductRepresentation	[0:1]	Reference to the representations of the product, being either a representation (IfcProductRepresentation) or as a special case a shape representations (IfcProductDefinitionShape). The product definition shape provides for multiple geometric representations of the shape property of the object within the same object coordinate system, defined by the object placement.	X
IfcElement
8	Tag	-		This attribute is out of scope for this model view definition and shall not be set.
	ConnectedTo	IfcRelConnectsElements @RelatingElement	S[0:?]	Reference to the element connection relationship. The relationship then refers to the other element to which this element is connected to.
	HasOpenings	IfcRelVoidsElement @RelatingBuildingElement	S[0:?]	Reference to the Voids Relationship that creates an opening in an element. An element can incorporate zero-to-many openings.	X
	IsConnectionRealization	IfcRelConnectsWithRealizingElements @RealizingElements	S[0:?]	Reference to the connection relationship with realizing element. The relationship then refers to the realizing element which provides the physical manifestation of the connection relationship.	X
	ConnectedFrom	IfcRelConnectsElements @RelatedElement	S[0:?]	Reference to the element connection relationship. The relationship then refers to the other element that is connected to this element.	X
	ContainedInStructure	IfcRelContainedInSpatialStructure @RelatedElements	S[0:1]	Containment relationship to the spatial structure element, to which the element is primarily associated.	X
IfcFeatureElement
IfcFeatureElementSubtraction
	VoidsElements	IfcRelVoidsElement @RelatedOpeningElement	[1:1]	Reference to the Voids Relationship that uses this Opening Element to create a void within an Element. The Opening Element can only be used to create a single void within a single Element.
IfcOpeningElement

Definitions applying to AISC Model View

Instance diagram

Concept usage

Properties on Occurences With Type

The Properties on Occurences With Type concept applies to this entity as shown in Table 6.

ObjectType	Property
BoltHole	AISC_EM11_Pset_Feature
BoltHole	AISC_EM11_Pset_BoltHole
SlotHole	AISC_EM11_Pset_Feature
SlotHole	AISC_EM11_Pset_Cope
Cope	AISC_EM11_Pset_Feature
Cope	AISC_EM11_Pset_SlotHole
Opening	AISC_EM11_Pset_Feature
Opening	AISC_EM11_Pset_Opening
SkewedEnd	AISC_EM11_Pset_Feature
SkewedEnd	AISC_EM11_Pset_SkewedEnd
WeldPreparation	AISC_EM11_Pset_Feature
WeldPreparation	AISC_EM11_Pset_WeldingPreparation
TubeChamfer	AIsC_EM11_Pset_TubeChamfer
TubeSaddle	AISC_EM11_Pset_TubeSaddle
TubeEdgeSaddle	AISC_EM11_Pset_TubeEdgeSaddle
TubeCrossingSaddle	AISC_EM11_Pset_TubeCrossingSaddle
TubeHoleSetIn	AISC_EM11_Pset_TubeHoleSetIn
TubeHoleSetOn	AISC_EM11_Pset_TubeHoleSetOn
TubeMitreHole	AISC_EM11_Pset_TubeMitreHole
TubeMitreSaddle	AISC_EM11_Pset_TubeMitreSaddle
TubeOblongHole	AISC_EM11_Pset_TubeOblongHole
TubeOffshoreSaddle	AISC_EM11_Pset_TubeOffshoreSaddle
TubeOffshoreChamfer	AISC_EM11_Pset_TubeOffshoreChamfer

Table 6 — IfcOpeningElement Properties on Occurences With Type

Exchange
Import	O
Export	O

Placement

The Placement concept applies to this entity.

Exchange
Import	R
Export	R

Geometry

The Geometry concept applies to this entity.

Concept alternates

Body Profile Extruded Area Solid

The Body Profile Extruded Area Solid concept applies to this entity.

Exchange
Import	O
Export	O

Body Brep Geometry PolyLoop

The Body Brep Geometry PolyLoop concept applies to this entity.

Exchange
Import	O
Export	O

Mapped Geometry

The Mapped Geometry concept applies to this entity.

Exchange
Import	O
Export	O

Concept inheritance

#	Concept	Model View
IfcOpeningElement
	Properties on Occurences With Type	AISC Model View
	Placement	AISC Model View
	Geometry	AISC Model View

Formal representations

XSD Specification

 <xs:element name="IfcOpeningElement" type="ifc:IfcOpeningElement" substitutionGroup="ifc:IfcFeatureElementSubtraction" nillable="true"/>

 <xs:complexType name="IfcOpeningElement">

  <xs:complexContent>

   <xs:extension base="ifc:IfcFeatureElementSubtraction"/>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcOpeningElement

 SUBTYPE OF (IfcFeatureElementSubtraction);

 INVERSE

END_ENTITY;

 EXPRESS-G diagram

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