IfcCovering

Semantic definitions at the entity

Entity definition

Definition from ISO 6707-1:1989: term used: Finishing - final coverings and treatments of surfaces and their intersections.

A covering is an element which covers some part of another element and is fully dependent on that other element. The IfcCovering defines the occurrence of a covering type, that (if given) is expressed by the IfcCoveringType.

EXAMPLEs include wall claddings, floorings and suspended ceilings as well as finish trim and base molding.

IFC2x PLATFORM CHANGE: The attribute PredefinedType is now optional and should only be inserted when there is no type information, given by IfcCoveringType, is assigned to the IfcCovering occurrence by IfcRelDefinesByType.

Coverings can be assigned to

a space represented by IfcSpace
- using the inverse relationship CoversSpaces pointing to IfcRelCoversSpaces. The space is then accessible via IfcRelCoversSpaces.RelatedSpace.
a space boundary represented by IfcRelSpaceBoundary
- using the inverse relationship ProvidesBoundaries pointing to IfcRelSpaceBoundary. The space is then accessible via IfcRelSpaceBoundary.RelatingSpace.
a building element represented by IfcBuildingElement
- using the inverse relationship Covers pointing to IfcRelCoversBldgElements. The building element is then accessible via IfcRelCoversBldgElements.RelatingBuildingElement.
a distribution element represented by IfcDistributionElement
- using the inverse relationship Covers pointing to IfcRelCoversBldgElements. The distribution element is then accessible via IfcRelCoversBldgElements.RelatingBuildingElement. Only IfcCovering's with a PredefinedType INSULATION, MEMBRANE, SLEEVING, or WRAPPING shall be used to cover distribution elements.

IFC2x PLATFORM CHANGE With the upward compatible platform extension at IfcRelCoversBldgElements the IfcCovering can now also cover an IfcElement (and its subtypes in addition to IfcBuildingElement). Additional enumerators have been added to IfcCoveringTypeEnum to identify coverings applicable to elements other than building elements.

The following guideline shall apply:

(default) if the space has coverings that may not have an own shape representation and no defined relationships to the building elements they cover, then the IfcCovering shall be assigned to IfcSpace using the IfcRelCoversSpaces relationship,
if the space has coverings that have an own shape representation and the space has defined space boundaries, then the covering, which relates to that space, may be assigned to the space boundaries using the link to IfcRelSpaceBoundary,
if the covering does not relate to a space, then the covering should be assigned to the building element or a distribution element using the IfcRelCoversBldgElements relationship.

HISTORY New entity in IFC Release 1.0.

Type Use Definition

The IfcCovering defines the occurrence of any covering, common information about covering types (or styles) is handled by IfcCoveringType. The IfcCoveringType (if present) may establish the common type name, usage (or predefined) type, common set of properties, common material layer set, and common shape representations (using IfcRepresentationMap). The IfcCoveringType is attached using the IfcRelDefinedByType.RelatingType objectified relationship and is accessible by the inverse IsDefinedBy attribute.

As an additional use agreement for standard coverings (i.e. slabs with constant thickness along the extrusion direction), the IfcCoveringType should have a unique IfcMaterialLayerSet, that is referenced by the IfcMaterialLayerSetUsage assigned to all occurrences of this covering type.

Material layer set and usage

Assignment of IfcMaterialLayerSetUsage and IfcMaterialLayerSet to the covering type and the covering occurrence.

If an IfcCoveringType is assigned to the IfcCovering, the attribute PredefinedType shall not be assigned, or shall be identical to IfcCoveringType.PredefinedType.

Property Set Use Definition:

The property sets relating to the IfcCovering 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 IfcCovering are part of this IFC release:

Pset_CoveringCommon: common property set for all covering occurrences
- Pset_CoveringCeiling: specific property set for all occurrences of coverings with the PredefinedType: CEILING
- Pset_CoveringFlooring: specific property set for all occurrences of coverings with the PredefinedType: FLOORING

Quantity Use Definition:

The quantities relating to the IfcCovering 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
GrossArea	Total area of the covering in the elevation view. The exact definition and calculation rules depend on the method of measurement used.	IfcQuantityArea
NetArea	Total area of the covering in the elevation view taking into account possible openings. The exact definition and calculation rules depend on the method of measurement used.	IfcQuantityArea

Geometry Use Definitions

The geometric representation of IfcCovering is given by the IfcProductDefinitionShape, allowing multiple geometric representation. Included are:

Local Placement

The local placement for IfcCovering 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 shall point (if given) to the same IfcSpatialStructureElement , which is used in the ContainedInStructure inverse attribute, or to a spatial structure element at a higher level, referenced by that.
If the IfcCovering, however, is assigned to an IfcBuildingElement, and this element defines its own local placement, than the PlacementRelTo relationship of IfcLocalPlacement shall point (if given) to the local placement of the IfcBuildingElement.
If the relative placement is not used, the absolute placement is defined within the world coordinate system.

Geometric Representations

The geometric representation of the IfcCovering depends on two criteria:

Does it define an area or a volume?
Is the base surface (either the IfcRelSpaceBoundary or the surface of the IfcBuildingElement it relates to) a planar surface or a cylindrical surface?

GeometricSet Representation

The 'GeometricSet' geometric representation of IfcCovering supports area definitions as 3D surfaces.

RepresentationIdentifier : 'Surface'
RepresentationType : 'GeometricSet'

The following additional constraints apply to the 'GeometricSet' representation of IfcCovering:

for planar base surfaces - bounded surface representation
for cylindrical base surfaces - swept surface representation

EXAMPLE for standard geometric representation.

The area of IfcCovering is given by an IfcPolyLoop for planar base surfaces (here given by the IfcRelSpaceBoundary).

The implicit planar surface of the IfcPolyLoop shall be identical with the planar surface defined by the IfcRelSpaceBoundary.

The area of the IfcCovering is given by an IfcSurfaceOfLinearExtrusion for cylindrical base surfaces (here given by the IfcRelSpaceBoundary - e.g. caused by a round wall).

The geometry representation of the IfcCovering is given by the IfcTrimmedCurve (the Curve parameter of the IfcArbitraryOpenProfileDef - in cases of faceted representation also an IfcPolyline). It is extruded within the plane of the base surface using the Depth parameter of the IfcSurfaceOfLinearExtrusion.

SweptSolid Representation

The 'SweptSolid' geometric representation of IfcCovering supports volume definitions as 3D solids.

RepresentationIdentifier : 'Body'
RepresentationType : 'SweptSolid'

The following additional constraints apply to the 'SweptSolid' representation of IfcCovering:

for planar base surfaces - swept area representation
for cylindrical base surfaces - swept area representation

EXAMPLE for advanced geometric representation.

The volume of IfcCovering is given by an IfcExtrudedAreaSolid for planar base surfaces (here given by the IfcRelSpaceBoundary).

The extruded area (IfcArbitraryClosedProfileDef) shall be coplanar to the surface defined by the IfcRelSpaceBoundary.

The volume of the IfcCovering is given by an IfcExtrudedAreaSolid for cylindrical base surfaces (here given by the IfcRelSpaceBoundary - e.g. caused by a round wall).

The geometry representation of the IfcCovering is given by the IfcCompositeCurve (the OuterCurve parameter of the IfcArbitraryClosedProfileDef - in cases of faceted representation also a closed IfcPolyline). It is extruded along the plane of the base surface using the Depth parameter of the IfcSurfaceOfLinearExtrusion.

Attribute definitions

#	Attribute	Type	Cardinality	Description	A
9	PredefinedType	-		This attribute is out of scope for this model view definition and shall not be set.

Formal Propositions

Rule	Description
WR61	Either the PredefinedType attribute is unset (e.g. because an IfcCoveringType is associated), or the inherited attribute ObjectType shall be given, if the PredefinedType is set to USERDEFINED.

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
IfcBuildingElement
IfcCovering
9	PredefinedType	-		This attribute is out of scope for this model view definition and shall not be set.

Definitions applying to AISC Model View

Instance diagram

Concept usage

Placement

The Placement concept applies to this entity.

Exchange
Import	O
Export	O

Properties on Occurrences

The Properties on Occurrences concept applies to this entity as shown in Table 2.

Property
AISC_EM11_Pset_SurfaceTreatment

Table 2 — IfcCovering Properties on Occurrences

Exchange
Import	O
Export	O

Geometry

The Geometry concept applies to this entity.

Exchange
Import	O
Export	O

Concept alternates

Patch Geometry

The Patch Geometry 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
IfcCovering
	Placement	AISC Model View
	Properties on Occurrences	AISC Model View
	Geometry	AISC Model View

Formal representations

XSD Specification

 <xs:element name="IfcCovering" type="ifc:IfcCovering" substitutionGroup="ifc:IfcBuildingElement" nillable="true"/>

 <xs:complexType name="IfcCovering">

  <xs:complexContent>

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

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcCovering

 SUBTYPE OF (IfcBuildingElement);

  PredefinedType : OPTIONAL IfcStrippedOptional;

 INVERSE

 WHERE

  WR61 : NOT(EXISTS(PredefinedType)) OR 
 (PredefinedType <> IfcCoveringTypeEnum.USERDEFINED) OR 
 ((PredefinedType = IfcCoveringTypeEnum.USERDEFINED) AND EXISTS (SELF\IfcObject.ObjectType));
END_ENTITY;

 EXPRESS-G diagram

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