IFC 4.3.x development

5.4.3.36 IfcOpeningElement

Change log

IFC4

additionsattributesPredefinedType

IFC4X3_RC3

additionswhere_rulesCorrectPredefinedType

5.4.3.36.1 Semantic definitions at the entity

The opening element stands for opening, recess or chase, all reflecting voids. It represents a void within any element that has physical manifestation. Openings can be inserted into walls, slabs, beams, columns, or other elements.

The IFC specification provides two entities for opening elements:

  • IfcOpeningStandardCase is used for all openings that have a constant profile along a linear extrusion. They are placed relative to the voided elements and the extrusion direction is perpendicular to the plane of the element (horizontally for walls, vertically for slabs). Only a single extrusion body is allowed. It cuts through the whole thickness of the voided element, i.e. it reflects a true opening.
  • IfcOpeningElement is used for all other occurrences of openings and in particular also for niches or recesses.

NOTE  View definitions or implementer agreements may restrict the types of elements which can be voided by an IfcOpeningElement or IfcOpeningStandardCase

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 attribute PredefinedType 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 PredefinedType is omitted, or the value is set to NOTDEFINED, no specific information of whether it is an opening or recess shall be assumed.

An IfcOpeningElement has to be inserted into an IfcElement by using the IfcRelVoidsElement relationship. It may be filled by an IfcDoor, IfcWindow, or another filling element by using the relationship IfcRelFillsElements. Depending on the type of the IfcShapeRepresentation of the IfcOpeningElement the voiding relationship implies:

  • if the IfcShapeRepresentation.<emRepresentationIdentifier = 'Body', then the Body shape represntation of the opening has to be subtracted from the body shape representation of the voided element - implicit Boolean difference operation.
  • if the IfcShapeRepresentation.<emRepresentationIdentifier = 'Reference', then the Reference shape representation of the opening is not subtracted, it is provided in addition to the hole in the Body shape representation of the voided element.

The IfcOpeningElement shall not participate in the containment relationship, i.e. it is not linked directly to the spatial structure of the project. It has a mandatory VoidsElements inverse relationship pointing to the IfcElement that is contained in the spatial structure.

  • The inverse relationship ContainedInStructure shall be NIL.

NOTE  See IfcRelVoidsElement for a diagram on how to apply spatial containment and the voiding relationship.

HISTORY  New entity in IFC1.0

IFC2x CHANGE  The intermediate ABSTRACT supertypes IfcFeatureElement and IfcFeatureSubtraction have been added.

IFC4 CHANGE  The attribute PredefinedType has been added at the end of attribute list. It should be used instead of the inherited attribute ObjectType from now on.

5.4.3.36.1 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.
IfcObjectDefinition
HasAssignments SET [0:?] OF IfcRelAssigns FOR RelatedObjects Reference to the relationship objects, that assign (by an association relationship) other subtypes of IfcObject to this object instance. Examples are the association to products, processes, controls, resources or groups.
Nests SET [0:1] OF IfcRelNests FOR RelatedObjects References to the decomposition relationship being a nesting. It determines that this object definition is a part within an ordered whole/part decomposition relationship. An object occurrence or type can only be part of a single decomposition (to allow hierarchical strutures only).

> IFC4 CHANGE  The inverse attribute datatype has been added and separated from Decomposes defined at IfcObjectDefinition.
IsNestedBy SET [0:?] OF IfcRelNests FOR RelatingObject References to the decomposition relationship being a nesting. It determines that this object definition is the whole within an ordered whole/part decomposition relationship. An object or object type can be nested by several other objects (occurrences or types).

> IFC4 CHANGE  The inverse attribute datatype has been added and separated from IsDecomposedBy defined at IfcObjectDefinition.
HasContext SET [0:1] OF IfcRelDeclares FOR RelatedDefinitions References to the context providing context information such as project unit or representation context. It should only be asserted for the uppermost non-spatial object.

> IFC4 CHANGE  The inverse attribute datatype has been added.
IsDecomposedBy SET [0:?] OF IfcRelAggregates FOR RelatingObject References to the decomposition relationship being an aggregation. It determines that this object definition is whole within an unordered whole/part decomposition relationship. An object definitions can be aggregated by several other objects (occurrences or parts).

> IFC4 CHANGE  The inverse attribute datatype has been changed from the supertype IfcRelDecomposes to subtype IfcRelAggregates.
Decomposes SET [0:1] OF IfcRelAggregates FOR RelatedObjects References to the decomposition relationship being an aggregation. It determines that this object definition is a part within an unordered whole/part decomposition relationship. An object definitions can only be part of a single decomposition (to allow hierarchical strutures only).

> IFC4 CHANGE  The inverse attribute datatype has been changed from the supertype IfcRelDecomposes to subtype IfcRelAggregates.
HasAssociations SET [0:?] OF IfcRelAssociates FOR RelatedObjects 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.
IfcObject
5 ObjectType OPTIONAL IfcLabel 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.
IsDeclaredBy SET [0:1] OF IfcRelDefinesByObject FOR RelatedObjects Link to the relationship object pointing to the declaring object that provides the object definitions for this object occurrence. The declaring object has to be part of an object type decomposition. The associated IfcObject, or its subtypes, contains the specific information (as part of a type, or style, definition), that is common to all reflected instances of the declaring IfcObject, or its subtypes.

> IFC4 CHANGE  New inverse relationship, change made with upward compatibility for file based exchange.
Declares SET [0:?] OF IfcRelDefinesByObject FOR RelatingObject Link to the relationship object pointing to the reflected object(s) that receives the object definitions. The reflected object has to be part of an object occurrence decomposition. The associated IfcObject, or its subtypes, provides the specific information (as part of a type, or style, definition), that is common to all reflected instances of the declaring IfcObject, or its subtypes.

> IFC4 CHANGE  New inverse relationship, change made with upward compatibility for file based exchange.
IsTypedBy SET [0:1] OF IfcRelDefinesByType FOR RelatedObjects Set of relationships to the object type that provides the type definitions for this object occurrence. The then associated IfcTypeObject, or its subtypes, contains the specific information (or type, or style), that is common to all instances of IfcObject, or its subtypes, referring to the same type.

> IFC4 CHANGE  New inverse relationship, the link to IfcRelDefinesByType had previously be included in the inverse relationship IfcRelDefines. Change made with upward compatibility for file based exchange.
IsDefinedBy SET [0:?] OF IfcRelDefinesByProperties FOR RelatedObjects Set of relationships to property set definitions attached to this object. Those statically or dynamically defined properties contain alphanumeric information content that further defines the object.

> IFC4 CHANGE  The data type has been changed from IfcRelDefines to IfcRelDefinesByProperties with upward compatibility for file based exchange.
IfcProduct
6 ObjectPlacement OPTIONAL IfcObjectPlacement 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.
7 Representation OPTIONAL IfcProductRepresentation 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.
ReferencedBy SET [0:?] OF IfcRelAssignsToProduct FOR RelatingProduct Reference to the IfcRelAssignsToProduct relationship, by which other products, processes, controls, resources or actors (as subtypes of IfcObjectDefinition) can be related to this product.
PositionedRelativeTo SET [0:?] OF IfcRelPositions FOR RelatedProducts
ReferencedInStructures SET [0:?] OF IfcRelReferencedInSpatialStructure FOR RelatedElements
IfcElement
8 Tag OPTIONAL IfcIdentifier The tag (or label) identifier at the particular instance of a product, e.g. the serial number, or the position number. It is the identifier at the occurrence level.
FillsVoids SET [0:1] OF IfcRelFillsElement FOR RelatedBuildingElement Reference to the IfcRelFillsElement Relationship that puts the element as a filling into the opening created within another element.
ConnectedTo SET [0:?] OF IfcRelConnectsElements FOR RelatingElement Reference to the element connection relationship. The relationship then refers to the other element to which this element is connected to.
IsInterferedByElements SET [0:?] OF IfcRelInterferesElements FOR RelatedElement Reference to the interference relationship to indicate the element that is interfered. The relationship, if provided, indicates that this element has an interference with one or many other elements.

> NOTE  There is no indication of precedence between IsInterferedByElements and InterferesElements.

> IFC4 CHANGE New inverse relationship.
InterferesElements SET [0:?] OF IfcRelInterferesElements FOR RelatingElement Reference to the interference relationship to indicate the element that interferes. The relationship, if provided, indicates that this element has an interference with one or many other elements.

> NOTE  There is no indication of precedence between IsInterferedByElements and InterferesElements.

> IFC4 CHANGE New inverse relationship.
HasProjections SET [0:?] OF IfcRelProjectsElement FOR RelatingElement Projection relationship that adds a feature (using a Boolean union) to the IfcBuildingElement.
HasOpenings SET [0:?] OF IfcRelVoidsElement FOR RelatingBuildingElement Reference to the IfcRelVoidsElement relationship that creates an opening in an element. An element can incorporate zero-to-many openings. For each opening, that voids the element, a new relationship IfcRelVoidsElement is generated.
IsConnectionRealizationSET [0:?] OF IfcRelConnectsWithRealizingElements FOR RealizingElementsReference to the connection relationship with realizing element. The relationship, if provided, assigns this element as the realizing element to the connection, which provides the physical manifestation of the connection relationship.
ProvidesBoundaries SET [0:?] OF IfcRelSpaceBoundary FOR RelatedBuildingElement Reference to space boundaries by virtue of the objectified relationship IfcRelSpaceBoundary. It defines the concept of an element bounding spaces.
ConnectedFrom SET [0:?] OF IfcRelConnectsElements FOR RelatedElement Reference to the element connection relationship. The relationship then refers to the other element that is connected to this element.
ContainedInStructure SET [0:1] OF IfcRelContainedInSpatialStructure FOR RelatedElements Containment relationship to the spatial structure element, to which the element is primarily associated. This containment relationship has to be hierachical, i.e. an element may only be assigned directly to zero or one spatial structure.
HasCoverings SET [0:?] OF IfcRelCoversBldgElements FOR RelatingBuildingElement Reference to IfcCovering by virtue of the objectified relationship IfcRelCoversBldgElement. It defines the concept of an element having coverings associated.
HasSurfaceFeatures SET [0:?] OF IfcRelAdheresToElement FOR RelatingElement Reference to the IfcRelAdheresToElement relationship that adheres a IfcSurfaceFeature to an element. An element can incorporate zero-to-many surface features in one relationship.
IfcFeatureElement
IfcFeatureElementSubtraction
VoidsElements IfcRelVoidsElement FOR RelatedOpeningElement 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
9 PredefinedType OPTIONAL IfcOpeningElementTypeEnum Predefined generic type for an opening that is specified in an enumeration. There may be a property set given specificly for the predefined types.

> IFC4 CHANGE The attribute has been added at the end of the entity definition.
HasFillings SET [0:?] OF IfcRelFillsElement FOR RelatingOpeningElement Reference to the Filling Relationship that is used to assign Elements as Fillings for this Opening Element. The Opening Element can be filled with zero-to-many Elements.

5.4.3.36.2 Entity inheritance

dot_inheritance IfcOpeningStandardCase IfcOpeningStandardCase IfcOpeningElement IfcOpeningElement IfcOpeningStandardCase->IfcOpeningElement IfcFeatureElementSubtraction IfcFeatureElementSubtraction IfcOpeningElement->IfcFeatureElementSubtraction IfcEarthworksCut IfcEarthworksCut IfcEarthworksCut->IfcFeatureElementSubtraction IfcFeatureElement IfcFeatureElement IfcFeatureElementSubtraction->IfcFeatureElement IfcVoidingFeature IfcVoidingFeature IfcVoidingFeature->IfcFeatureElementSubtraction IfcFeatureElementAddition IfcFeatureElementAddition IfcFeatureElementAddition->IfcFeatureElement IfcElement IfcElement IfcFeatureElement->IfcElement IfcSurfaceFeature IfcSurfaceFeature IfcSurfaceFeature->IfcFeatureElement IfcElement_children 10 more... IfcElement_children->IfcElement IfcProduct IfcProduct IfcElement->IfcProduct IfcProduct_children 8 more... IfcProduct_children->IfcProduct IfcObject IfcObject IfcProduct->IfcObject IfcObject_children 5 more... IfcObject_children->IfcObject IfcObjectDefinition IfcObjectDefinition IfcObject->IfcObjectDefinition IfcContext IfcContext IfcContext->IfcObjectDefinition IfcRoot IfcRoot IfcObjectDefinition->IfcRoot IfcTypeObject IfcTypeObject IfcTypeObject->IfcObjectDefinition IfcPropertyDefinition IfcPropertyDefinition IfcPropertyDefinition->IfcRoot IfcRelationship IfcRelationship IfcRelationship->IfcRoot

5.4.3.36.3 Definitions applying to General Usage

5.4.3.36.3.1 Body AdvancedBrep Geometry

An IfcElement (so far no further constraints are defined at the level of its subtypes or by view definitions) may be represented as a single or multiple boundary representation models, which include advanced surfaces, usually refered to as NURBS surfaces. The 'AdvancedBrep' representation allows for the representation of complex free-form element shape.

NOTE  View definitions or implementer agreements may restrict or disallow the use of 'AdvancedBrep' geometry.

5.4.3.36.3.2 Body Brep Geometry

Any IfcElement (so far no further constraints are defined at the level of its subtypes) may be represented as a single or multiple Boundary Representation models (which are restricted to be faceted Brep's with or without voids). The Brep representation allows for the representation of complex element shape.

 

Brep representation
EXAMPLE  As shown in Figure 150, the Brep representation is given by an IfcShapeRepresentation, which includes one or more items, all of type IfcFacetedBrep. In some cases it may be useful to also expose a simple representation as a bounding box representation of the same complex shape.

Figure 150 — Building element body boundary representation

 

5.4.3.36.3.3 Body CSG Geometry

Any IfcElement (so far no further constraints are defined at the level of its subtypes) may be represented a CSG primitive or CSG tree. The CSG representation allows for the representation of complex element shape.

NOTE  View definitions or implementer agreements may restrict or disallow the use of 'CSG' geometry.

5.4.3.36.3.4 Body Geometry

The 'Body' representation of IfcOpeningElement can be represented using the representation types 'SweptSolid', and 'Brep'. The representation type 'Brep' is explained at IfcFeatureElement

Swept Solid Representation Type 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:

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

Figure 160 illustrates an opening with horizontal extrusion.

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

Figure 160 — Opening with full extrusion

Figure 161 illustrates an opening for a recess.

NOTE  The local placement directions for the IfcOpeningElement are only given as an example, other directions are valid as well.
NOTE  Rectangles are now defined centric, the placement location has to be set:
recess

Figure 161 — Opening with recess extrusion

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:

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.

Figure 162 shows a vertical extrusion with multiple extrusion bodies for the opening. Each extrusion body has a different extrusion lenght.

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

Figure 162 — Opening with multiple extrusions

5.4.3.36.3.5 Body SurfaceModel Geometry

Any IfcElement (so far no further constraints are defined at the level of its subtypes) may be represented as a single or multiple surface models, based on either shell or face based surface models. It may also include tessellated models.

 

surface model
EXAMPLE  As shown in Figure 149, the surface model representation is given by an IfcShapeRepresentation, which includes a single item which is either an IfcShellBasedSurfaceModel, or an IfcFaceBasedSurfaceModel. In some cases it may also be useful to expose a simple representation as a bounding box representation of the same complex shape.

Figure 149 — Element surface model representation

 

5.4.3.36.3.6 Body SurfaceOrSolidModel Geometry

Any IfcElement (so far no further constraints are defined at the level of its subtypes) may be represented as a mixed representation, including surface and solid models.

5.4.3.36.3.7 Body Tessellation Geometry

Any IfcElement (so far no further constraints are defined at the level of its subtypes) may be represented as a single or multiple tessellated surface models, in particular triangulated surface models.

5.4.3.36.3.8 Box Geometry

bounding box
EXAMPLE  Any IfcElement may be represented by a bounding box, which shows the maximum extend of the body within the object coordinate system established by the IfcObjectPlacement. As shown in Figure 148, the bounding box representation is given by an IfcShapeRepresentation that includes a single item, an IfcBoundingBox.

Figure 148 — Building element box representation

 

5.4.3.36.3.9 Classification Association

Any object occurrence or object type can have a reference to a specific classification reference, i.e. to a particular facet within a classification system.

5.4.3.36.3.10 CoG Geometry

The 'CoG', Center of Gravity, shape representation is used as a means to verify the correct import by comparing the CoG of the imported geometry with the explicily provided CoG created during export.

5.4.3.36.3.11 Element Projecting

5.4.3.36.3.12 Element Voiding

5.4.3.36.3.13 FootPrint Geometry

Type Identifier
'GeometricCurveSet''FootPrint'
'Annotation2D' 'FootPrint'

5.4.3.36.3.14 Identity

IfcRoot assigns the globally unique ID. In addition it may provide for a name and a description about the concept.

5.4.3.36.3.15 Mapped Geometry

Any IfcElement (so far no further constraints are defined at the level of its subtypes) may be represented using the 'MappedRepresentation'. This shall be supported as it allows for reusing the geometry definition of a type at all occurrences of the same type. The results are more compact data sets.

The same constraints, as given for 'SurfaceOrSolidModel', 'SurfaceModel', 'Tessellation', 'Brep', and 'AdvancedBrep' geometric representation, shall apply to the IfcRepresentationMap.

5.4.3.36.3.16 Object Predefined Type

5.4.3.36.3.17 Object Typing

Any object occurrence can be typed by being assigned to a common object type utilizing this concept. A particular rule, restricting the applicable subtypes of IfcTypeObject that can be assigned, is introduced by overriding this concept at the level of subtypes of IfcObject.

5.4.3.36.3.18 Object User Identity

An attribute Name and optionally Description can be used for all subypes of IfcObject. For those subtypes, that have an object type definition, such as ifcBeam - IfcBeamType, the common Name and optionally Description is associated with the object type.

5.4.3.36.3.19 Product Geometric Representation

The geometric representation of any IfcProduct is provided by the IfcProductDefinitionShape allowing multiple geometric representations. It uses the Product Placement concept utilizing IfcLocalPlacement to establish an object coordinate system, within all geometric representations are founded.

NOTE  A detailed specification of how to apply the local placement and which shape representaions are applicable is provided at the level of subtypes of IfcProduct and is further determined by the model view definition and implementer agreements.

5.4.3.36.3.20 Product 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.
HasPlacement
'IfcLocalPlacement'
'IfcLocalPlacement'

5.4.3.36.3.21 Product Placement

The Product Placement establishes the object coordinate system and is required, if a geometric shape representation is provided for this product.

5.4.3.36.3.22 Property Sets for Objects

PsetName
'Pset_OpeningElementCommon'
'Pset_EnvironmentalImpactIndicators'
'Pset_EnvironmentalImpactValues'
'Pset_Condition'
'Pset_ManufacturerOccurrence'
'Pset_ManufacturerTypeInformation'
'Pset_ServiceLife'
'Pset_Warranty'

5.4.3.36.3.23 Property Sets with Override

Any object occurrence can hold property sets, either directly at the object occurrence as element specific property sets, or at the object type, as type property sets. In this case, the properties that are provided to the object occurrence are the combinations of element specific and type properties. In case, that the same property (within the same property set, is defined both, in occurrence and type properties, the property value of the occurrence property overrides the property value of the type property.

5.4.3.36.3.24 Quantity Sets

QsetName
'Qto_OpeningElementBaseQuantities'

5.4.3.36.3.25 Reference Geometry

Since there are no Boolean operations, either as IfcBooleanResult or implicitly by IfcRelVoidsElement the geometry of the IfcOpeningElement shall not be used to subtract the opening from the 'Body' shape representation of the voided element.

5.4.3.36.3.26 Revision Control

Ownership, history, and merge state is captured using IfcOwnerHistory.

5.4.3.36.3.27 Spatial Containment

As a subordinate part being fully dependent on the master element the IfcFeatureElement shall have no independent containment relationship to the spatial structure.

  • The SELF\IfcElement.ContainedInStructure relationship shall be NIL.

5.4.3.36.4 Formal representations

ENTITY IfcOpeningElement
 SUPERTYPE OF (ONEOF
	(IfcOpeningStandardCase))
 SUBTYPE OF (IfcFeatureElementSubtraction);
	PredefinedType : OPTIONAL IfcOpeningElementTypeEnum;
 INVERSE
	HasFillings : SET [0:?] OF IfcRelFillsElement FOR RelatingOpeningElement;
 WHERE
	CorrectPredefinedType : NOT(EXISTS(PredefinedType)) OR
(PredefinedType <> IfcOpeningElementTypeEnum.USERDEFINED) OR
((PredefinedType = IfcOpeningElementTypeEnum.USERDEFINED) AND EXISTS(SELF\IfcObject.ObjectType));
END_ENTITY;