Approvals may be associated to indicate the status of acceptance or rejection using the IfcRelAssociatesApproval relationship where RelatingApproval refers to an IfcApproval and RelatedObjects contains the IfcActionRequest. Approvals may be split into sub-approvals using IfcApprovalRelationship to track approval status separately for each party where RelatingApproval refers to the higher-level approval and RelatedApprovals contains one or more lower-level approvals. The hierarchy of approvals implies sequencing such that a higher-level approval is not executed until all of its lower-level approvals have been accepted.

As shown in Figure 1, an IfcActionRequest may be aggregated into components.

Figure 1 — Action request composition

As shown in Figure 1, an IfcActionRequest may be assigned to the following entities using relationships as indicated:

• IfcActor (IfcRelAssignsToActor): Person or organization issuing the request such as a tenant or owner.

The IfcActionRequest may have assignments of its own using the IfcRelAssignsToControl relationship where RelatingControl refers to the IfcActionRequest and RelatedObjects contains one or more objects of the following types:

• IfcActor: Person or organization(s) fulfilling the request such as a facilities manager or contractor.

Figure 1 — Action request assignment

The operating function of an asset within an organization may be particularly valuable in situations where one organization provides and maintains core services and another organization adds and maintains terminal services. It can classify who owns and is responsible for the asset. Operating function can be designated through the use of one or more classification references.

The IfcBeam, as any subtype of IfcBuildingElement, may participate alternatively in one of the two different containment relationships:

• the Spatial Containment (defined here), or
• the Element Composition.

The material of the IfcBeam is defined by the IfcMaterialProfileSet or as fallback by IfcMaterial, and it is attached either directly or at the IfcBeamType.

NOTE  It is illegal to assign an IfcMaterialProfileSetUsage to an IfcBeam. Only the subtype IfcBeamStandardCase supports this concept.

The 'Axis' 'Curve 3D' geometry can be used to represent the system axis and length of a beam that may extent the body length.

NOTE  The 'Axis' is not used to locate the material profile set, only the subtype IfcBeamStandardCase provides this capability.

The following additional constraints apply to the 'SweptSolid' representation type:

• Solid: IfcExtrudedAreaSolid, IfcRevolvedAreaSolid shall be supported
• Profile: all subtypes of IfcProfileDef (with exception of IfcArbitraryOpenProfileDef)
• Extrusion:  All extrusion directions shall be supported.

Figure 1 illustrates the 'SweptSolid' geometric representation. There are no restrictions or conventions on how to use the local placement (black), solid of extrusion placement (red) and profile placement (green).

Figure 1 — Beam swept solid

Figure 2 illustrates the use of non-perpendicular extrusion to create the IfcExtrudedAreaSolid.

Figure 2 — Beam non-perpendicular extrusion

The following additional constraints apply to the 'AdvancedSweptSolid' representation type:

• Solid: IfcSurfaceCurveSweptAreaSolid, IfcFixedReferenceSweptAreaSolid, IfcExtrudedAreaSolidTapered, IfcRevolvedAreaSolidTapered shall be supported.

NOTE  View definitions and implementer agreement can further constrain the allowed swept solid types.

• Profile: see 'SweptSolid' geometric representation
• Extrusion: not applicable

The following additional constraints apply to the 'Clipping' representation type:

• Solid: see 'SweptSolid' geometric representation
• Profile: see 'SweptSolid' geometric representation
• Extrusion: see 'SweptSolid' geometric representation
• Boolean result: The IfcBooleanClippingResult shall be supported, allowing for Boolean differences between the swept solid (here IfcExtrudedAreaSolid) and one or several IfcHalfSpaceSolid (or its subtypes).

Figure 1 illustrates use of IfcBooleanClippingResult between an IfcExtrudedAreaSolid and an IfcHalfSpaceSolid to create a clipped body.

Figure 1 — Beam clipping

The IfcBeamStandardCase defines in addition that the IfcBeamType should have a unique IfcMaterialProfileSet, that is referenced by the IfcMaterialProfileSetUsage that is assigned to all occurrences of this IfcBeamType.

	EXAMPLE  Figure 1 illustrates assignment of IfcMaterialProfileSetUsage and IfcMaterialProfileSet to the IfcBeamStandardCase as the beam occurrence and to the IfcBeamType. The same IfcMaterialProfileSet shall be shared by many occurrences of IfcMaterialProfileSetUsage. This relationship shall be consistent to the relationship between the IfcBeamType and the IfcBeamStandardCase.
Figure 1 — Beam profile usage

<blockquote class="example">EXAMPLE&nbsp; Figure 2 illustrates alignment of cardinal points.</blockquote> NOTE  It has to be guaranteed that the use of IfcCardinalPointEnum is consistent to the placement of the extrusion body provided by IfcExtrudedAreaSolid.Position NOTE  The cardinal points 8 (top centre) and 6 (mid-depth right) are assigned according to the definition at IfcCardinalPointReference

Figure 2 — Beam cardinal points

	EXAMPLE  Figure 3 illustrates assignment of a composite profile by using IfcCompositeProfile for geometric representation and several IfcMaterialProfile's within the IfcMaterialProfileSet.
Figure 3 — Beam composite profiles

The following restriction is imposed:

• The local placement shall provide the location and directions for the standard beam, the x/y plane is the plane for the start profile, and the z-axis is the extrusion axis for the beam body (in case of rotation, the tangent direction).

The following additional constraints apply to the 'Axis' representation, if the 'Body' shape representation has the RepresentationType : 'SweptSolid':

• Axis
  • IfcPolyline having two Points, or IfcTrimmedCurve with BasisCurve of Type IfcLine for 'SweptSolid' provided as IfcExtrudedAreaSolid. The axis curve lies on the z axis of the object coordinate system.
  • IfcTrimmedCurve with BasisCurve of Type IfcCircle for 'SweptSolid' provided as IfcRevolvedAreaSolid. The axis curve lies on the x/z plane of the object coordinate system, the tangent at the start is along the positive z-axis.

	EXAMPLE  As shown in Figure 76, the axis shall be defined along the z axis of the object coordinate system. The axis representation can be used to represent the system length of a beam that may extent the body length of the beam.
Figure 1 — Beam axis representation

EXAMPLE  As shown in Figure 77, the axis representation shall be used to represent the cardinal point as the offset between the 'Axis' and the extrusion path of the beam. The extrusion path is provided as IfcExtrudedAreaSolid.ExtrudedDirection and should be parallel to the 'Axis' and the z axis. It has to be guaranteed that the value provided by IfcMaterialProfileSetUsage.CardinalPoint is consistent to the IfcExtrudedAreaSolid.Position.

Figure 2 — Beam axis cardinal point

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

• Solid: IfcExtrudedAreaSolid, IfcRevolvedAreaSolid shall be supported
• Solid Position : The IfcSweptAreaSolid.Position shall exclusively been used to correspond to the cardinal point. The x/y offset of the Position represents the cardinal point offset of the profile against the axis. No rotation shall be allowed.
• Profile: All subtypes of IfcParameterizedProfileDef
• Profile Position : For all single profiles, the IfcParameterizedProfileDef.Position shall be NIL, or having Location = 0.,0. and RefDirection = 1.,0.
• Extrusion: Perpendicular to the profile direction. The IfcExtrudedAreaSolid.ExtrudedDirection shall be [0.,0.,1.].
• Orientation: The y-axis of the profile, as determined by IfcSweptAreaSolid.Position.P[2] shall point upwards. It indicates the "role" of the beam, a role=0° means y-axis of profile pointing upwards.

Figure 1 illustrates a standard geometric representation with cardinal point applied as 1 (bottom left).

The following interpretation of dimension parameter applies for rectangular beams with linear extrusions:

• IfcRectangleProfileDef.YDim interpreted as beam height
• IfcRectangleProfileDef.XDim interpreted as beam width

The following interpretation of dimension parameter applies for circular beams:

• IfcCircleProfileDef.Radius interpreted as beam radius.

Figure 1 — Beam body extrusion

The following additional constraints apply to the 'AdvancedSweptSolid' representation type:

• Solid: IfcSurfaceCurveSweptAreaSolid, IfcFixedReferenceSweptAreaSolid, IfcExtrudedAreaSolidTapered, IfcRevolvedAreaSolidTapered shall be supported.

NOTE  View definitions and implementer agreement can further constrain the allowed swept solid types.

• Solid Position : see 'SweptSolid' geometric representation
• Profile: see 'SweptSolid' geometric representation
• Profile Position : see 'SweptSolid' geometric representation
• Extrusion: not applicable

The following constraints apply to the 'Clipping' representation:

• Solid : see 'SweptSolid' geometric representation
• Solid Position : see 'SweptSolid' geometric representation
• Profile : see 'SweptSolid' geometric representation
• Profile Position : see 'SweptSolid' geometric representation
• Extrusion : see 'SweptSolid' geometric representation
• Orientation : see 'SweptSolid' geometric representation
• Boolean result: The IfcBooleanClippingResult shall be supported, allowing for Boolean differences between the swept solid (here IfcExtrudedAreaSolid) and one or several IfcHalfSpaceSolid (or its subtypes).

Figure 1 illustrates a 'Clipping' geometric representation with use of IfcBooleanClippingResult between an IfcExtrudedAreaSolid and an IfcHalfSpaceSolid to create a clipped body, with cardinal point applied as 4 (mid-depth left)

Figure 1 — Beam body clipping

The material of the IfcBeamType is defined by the IfcMaterialProfileSet or as fall back by IfcMaterial and attached by the IfcRelAssociatesMaterial.RelatingMaterial. It is accessible by the inverse HasAssociations relationship.

NOTE  It is illegal to assign an IfcMaterial to an IfcBeamType, if there is at least one occurrence of IfcBeamStandardCase for this type.

The shared profile definition is defined by assigning an IfcMaterialProfileSet (see material use definition above). The IfcMaterialProfile refers to the subtype of IfcProfileDef that is the common profile for all beam occurrence, if used. It is only applicable if the IfcBeamType has only occurrences of type IfcBeamStandardCase (see definition of IfcBeamStandardCase for further information).

NOTE  The attribute ProfileName of the IfcProfileDef subtype, referenced in IfcMaterialProfile should contain a standardized profile name according to local standards. However, an additional geometric representation of the profile is necessary (such as IfcExtrudedAreaSolid). An importing application is allowed to check for the existence of the profile name: in case of identifying it as a standardized name, the corresponding profile geometry and possibly other cross sectional properties can be read from a library. Otherwise the geometric representation and possible non geometric IfcProfileProperties have to be used.

The IfcBeamType may define the shared geometric representation for all beam occurrences. The RepresentationMaps attribute refers to a list of IfcRepresentationMap's, that allow for multiple geometric representations (e.g. with IfcShaperepresentation's having an RepresentationIdentifier 'Box', 'Axis', or 'Body'). It is only applicable if the IfcBeamType has only occurrences of type IfcBeam (See geometric use definition of IfcBeam for further information).

NOTE  If the IfcBeamType has an associated IfcMaterialProfileSet, then no shared geometric representation shall be provided.

NOTE  The product shape representations are defined as RepresentationMaps (attribute of the supertype IfcTypeProduct), which get assigned by an element occurrence instance through the IfcShapeRepresentation.Item[n] being an IfcMappedItem. See IfcTypeProduct for further information.

NOTE  The values of attributes RepresentationIdentifier and RepresentationType of IfcShapeRepresentation are restricted in the same way as those for IfcBeam and IfcBeamStandardCase

NOTE  By using the inverse relationship IfcBridge.Decomposes it references IfcProject || IfcSite || IfcBridge through IfcRelAggregates.RelatingObject. If it refers to another instance of IfcBridge, the referenced IfcBridge needs to have a different and higher CompositionType, i.e. COMPLEX (if the other IfcBuilding has ELEMENT), or ELEMENT (if the other IfcBridge has PARTIAL).

NOTE  By using the inverse relationship IfcBridge.IsDecomposedBy it references IfcBridge || IfcBridgePart through IfcRelAggregates.RelatedObjects. If it refers to another instance of IfcBridge, the referenced IfcBridge needs to have a different and lower CompositionType, i.e. ELEMENT (if the other IfcBridge has COMPLEX), or PARTIAL (if the other IfcBridge has ELEMENT).

NOTE  If there are building elements and/or other elements directly related to the IfcBridge, they are associated with the IfcBridge by using the objectified relationship IfcRelContainedInSpatialStructure. The IfcBridge references them by its inverse relationship: > * IfcBridge.ContainsElements -- referencing any subtype of IfcProduct (with the exception of other spatial structure element) by IfcRelContainedInSpatialStructure.RelatedElements.

The local placement for IfcBridge is defined in its supertype IfcProduct. It is defined by IfcLocalPlacement or by IfcLinearPlacement>/em> which defines the local coordinate system that is referenced by all geometric representations.

• The PlacementRelTo relationship of IfcLocalPlacement shall point (if relative placement is used) to the IfcSpatialStructureElement of type IfcSite, or of type IfcBuilding (e.g. to position a building relative to a building complex, or a building section to a building).
• If the relative placement is not used, the absolute placement is defined within the world coordinate system.

The body (or solid model) geometric representation (if the bridge has an independent geometric representation) of IfcBridge is defined using faceted B-Rep capabilities (with or without voids), based on the IfcFacetedBrep or on the IfcFacetedBrepWithVoids. In the case of alignment based infrastructure, the geometric representation can be defined using IfcSectionedSolidHorizontal optionally IfcSweptAreaSolid.

NOTE  Since the bridge shape is usually described by the exterior building elements, an independent shape representation shall only be given, if the bridge is exposed independently from its constituting elements and such independent geometric representation may be prohibited in model view definitions.

NOTE  By using the inverse relationship IfcBridgePart.Decomposes it references (IfcBridge || IfcBridgePart) through IfcRelAggregates.RelatingObject_IfcBridgePart, the referenced IfcBridgePart needs to have a different and higher CompositionType, i.e. COMPLEX (if the other IfcBridgePart has ELEMENT), or ELEMENT (if the other IfcBridgePart has PARTIAL)._

NOTE  By using the inverse relationship IfcBridgePart.IsDecomposedBy it references IfcBridgePart through IfcRelAggregates.RelatedObjects. If it refers to another instance of IfcBridgePart, the referenced IfcBridgePart needs to have a different and lower CompositionType, i.e. ELEMENT (if the other IfcBuildingStorey has COMPLEX), or PARTIAL (if the other IfcBuildingStorey has ELEMENT).

NOTE  Multi storey spaces shall be spatially contained by only a single building storey, usually it is the building storey where the base of the space lies.

If there are building elements and/or other elements directly related to the IfcBridgePart (like most building elements, such as walls, columns, etc.), they are associated with the IfcBridgePart by using the objectified relationship IfcRelContainedInSpatialStructure. The IfcBridgePart references them by its inverse relationship:

• IfcBridgePart.ContainsElements -- referencing any subtype of IfcProduct (with the exception of other spatial structure element) by IfcRelContainedInSpatialStructure.RelatedElements.

Elements can also be referenced in an IfcBridgePart, for example, if they span through several storeys. This is expressed by using the objectified relationship IfcRelReferencedInSpatialStructure. Systems, such as building service or electrical distribution systems, zonal systems, or structural analysis systems, relate to IfcBridgePart by using the objectified relationship IfcRelServicesBuildings.

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

• The PlacementRelTo relationship of IfcLocalPlacement or IfcLinearPlacement shall point (if relative placement is used) to the IfcSpatialStructureElement of type IfcBridge, or of type IfcBridgePart (e.g. to position a bridge part relative to a bridge part complex, or a partial bridge part to a bridge part).
• If the relative placement is not used, the absolute placement is defined within the world coordinate system.

The body (or solid model) geometric representation (if the bridge part has an independent geometric representation) of IfcBridgePart is defined using faceted B-Rep capabilities (with or without voids), based on the IfcFacetedBrep or on the IfcFacetedBrepWithVoids. In the case of alignment based infrastructure, the geometric representation can be defined using IfcSectionedSolidHorizontal optionally IfcSweptAreaSolid.

NOTE  Since the bridge part shape is usually described by the exterior building elements, an independent shape representation shall only be given, if the bridge part is exposed independently from its constituting elements and such independent geometric representation may be prohibited in model view definitions.

NOTE  By using the inverse relationship IfcBuilding.Decomposes it references IfcProject || IfcSite || IfcBuilding through IfcRelAggregates.RelatingObject. If it refers to another instance of IfcBuilding, the referenced IfcBuilding needs to have a different and higher CompositionType, i.e. COMPLEX (if the other IfcBuilding has ELEMENT), or ELEMENT (if the other IfcBuilding has PARTIAL).

NOTE  By using the inverse relationship IfcBuilding.IsDecomposedBy it references IfcBuilding || IfcBuildingStorey through IfcRelAggregates.RelatedObjects. If it refers to another instance of IfcBuilding, the referenced IfcBuilding needs to have a different and lower CompositionType, i.e. ELEMENT (if the other IfcBuilding has COMPLEX), or PARTIAL (if the other IfcBuilding has ELEMENT).

NOTE  If there are building elements and/or other elements directly related to the IfcBuilding (like a curtain wall spanning several stories), they are associated with the IfcBuilding by using the objectified relationship IfcRelContainedInSpatialStructure. The IfcBuilding references them by its inverse relationship: > * IfcBuilding.ContainsElements -- referencing any subtype of IfcProduct (with the exception of other spatial structure element) by IfcRelContainedInSpatialStructure.RelatedElements.

The local placement for IfcBuilding 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 relative placement is used) to the IfcSpatialStructureElement of type IfcSite, or of type IfcBuilding (e.g. to position a building relative to a building complex, or a building section to a building).
• If the relative placement is not used, the absolute placement is defined within the world coordinate system.

The foot print representation of IfcBuilding is given by either a single 2D curve (such as IfcPolyline or IfcCompositeCurve), or by a list of 2D curves (in case of inner boundaries), if the building has an independent geometric representation.

NOTE  The independent geometric representation of IfcBuilding may not be allowed in certain model view definitions. In those cases only the contained elements and spaces have an independent geometric representation.

The body (or solid model) geometric representation (if the building has an independent geometric representation) of IfcBuilding is defined using faceted B-Rep capabilities (with or without voids), based on the IfcFacetedBrep or on the IfcFacetedBrepWithVoids.

NOTE  Since the building shape is usually described by the exterior building elements, an independent shape representation shall only be given, if the building is exposed independently from its constituting elements and such independent geometric representation may be prohibited in model view definitions.

NOTE  The IfcBuildingElementProxyType can be used to share common information among many occurrences of the same proxy without establishing a particular semantic meaning of the type.

If no IfcBuildingElementProxyType is attached (i.e. if only occurrence information is available) the PredefinedType should be provided. If set to .USERDEFINED. a user defined value has to be provided by the ObjectType attribute.

The material of the IfcBuildingElementProxy is defined by IfcMaterial and attached by the IfcRelAssociatesMaterial.RelatingMaterial. It is accessible by the inverse HasAssociations relationship.

NOTE  It is illegal to assign an IfcMaterial to an IfcBuildingElementProxy with the PredefinedType = ProvisionForVoid.

Material information can also be given at the IfcBuildingElementProxyType, defining the common attribute data for all occurrences of the same type. It is then accessible by the inverse IsTypedBy relationship pointing to IfcBuildingElementProxyType.HasAssociations and via IfcRelAssociatesMaterial.RelatingMaterial to IfcMaterial. If both are given, then the material directly assigned to IfcBuildingElementProxy overrides the material assigned to IfcBuildingElementProxyType.

The IfcBuildingElementProxy, as any subtype of IfcBuildingElement, may participate alternatively in one of the two different containment relationships:

• the Spatial Containment (defined here), or
• the Element Composition.

NOTE  By using the inverse relationship IfcBuildingStorey.Decomposes it references (IfcBuilding || IfcBuildingStorey) through IfcRelAggregates.RelatingObject_IfcBuildingStorey, the referenced IfcBuildingStorey needs to have a different and higher CompositionType, i.e. COMPLEX (if the other IfcBuildingStorey has ELEMENT), or ELEMENT (if the other IfcBuildingStorey has PARTIAL)._

NOTE  By using the inverse relationship IfcBuildingStorey.IsDecomposedBy it references IfcBuildingStorey || IfcSpace through IfcRelAggregates.RelatedObjects. If it refers to another instance of IfcBuildingStorey, the referenced IfcBuildingStorey needs to have a different and lower CompositionType, i.e. ELEMENT (if the other IfcBuildingStorey has COMPLEX), or PARTIAL (if the other IfcBuildingStorey has ELEMENT).

NOTE  Multi storey spaces shall be spatially contained by only a single building storey, usually it is the building storey where the base of the space lies.

If there are building elements and/or other elements directly related to the IfcBuildingStorey (like most building elements, such as walls, columns, etc.), they are associated with the IfcBuildingStorey by using the objectified relationship IfcRelContainedInSpatialStructure. The IfcBuildingStorey references them by its inverse relationship:

• IfcBuildingStorey.ContainsElements -- referencing any subtype of IfcProduct (with the exception of other spatial structure element) by IfcRelContainedInSpatialStructure.RelatedElements.

Elements can also be referenced in an IfcBuildingStorey, for example, if they span through several storeys. This is expressed by using the objectified relationship IfcRelReferencedInSpatialStructure. Systems, such as building service or electrical distribution systems, zonal systems, or structural analysis systems, relate to IfcBuildingStorey by using the objectified relationship IfcRelServicesBuildings.

The local placement for IfcBuildingStorey 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 relative placement is used) to the IfcSpatialStructureElement of type IfcBuilding, or of type IfcBuildingStorey (e.g. to position a building storey relative to a building storey complex, or a partial building storey to a building storey).
• If the relative placement is not used, the absolute placement is defined within the world coordinate system.

The foot print representation of IfcBuildingStorey is given by either a single 2D curve (such as IfcPolyline or IfcCompositeCurve), or by a list of 2D curves (in case of inner boundaries), if the building storey has an independent geometric representation.

NOTE  The independent geometric representation of IfcBuildingStorey may not be allowed in certain model view definitions. In those cases only the contained elements and spaces have an independent geometric representation.

The body (or solid model) geometric representation (if the building storey has an independent geometric representation) of IfcBuildingStorey is defined using faceted B-Rep capabilities (with or without voids), based on the IfcFacetedBrep or on the IfcFacetedBrepWithVoids.

NOTE  Since the building storey shape is usually described by the exterior building elements, an independent shape representation shall only be given, if the building storey is exposed independently from its constituting elements and such independent geometric representation may be prohibited in model view definitions.

Some IfcBuildingElement may be represented by an surface as an abstract geometric representation. See each subtype for specific guidance.

The IfcChimney, as any subtype of IfcBuildingElement, may participate alternatively in one of the two different containment relationships:

• the Spatial Containment (defined here), or
• the Element Composition.

The material of the IfcColumn is defined by the IfcMaterialProfileSet or as fallback by IfcMaterial, and it is attached either directly or at the IfcColumnType.

NOTE  It is illegal to assign an IfcMaterialProfileSetUsage to an IfcColumn. Only the subtype IfcColumnStandardCase supports this concept.

The IfcColumn, as any subtype of IfcBuildingElement, may participate alternatively in one of the two different containment relationships:

• the Spatial Containment (defined here), or
• the Element Composition.

The axis representation can be used to represent the system length of a column that may extent the body length of the column.

NOTE  The 'Axis' is not used to locate the material profile set, only the subtype IfcColumnStandardCase provides this capability.

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

• Solid: IfcExtrudedAreaSolid, IfcRevolvedAreaSolid shall be supported
• Profile: all subtypes of IfcProfileDef (with exception of IfcArbitraryOpenProfileDef) 
• Extrusion: All extrusion directions shall be supported

Figure 1 illustrates a 'SweptSolid' geometric representation. There are no restrictions or conventions on how to use the local placement (black), solid of extrusion placement (red) and profile placement (green).

Figure 1 — Column swept solid

Figure 2 illustrates use of a special profile type (here IfcIShapeProfileDef) for the definition of the IfcExtrudedAreaSolid.

Figure 2 — Column extrusion of I-Shape

The following additional constraints apply to the 'AdvancedSweptSolid' representation type:

• Solid: IfcSurfaceCurveSweptAreaSolid, IfcFixedReferenceSweptAreaSolid, IfcExtrudedAreaSolidTapered, IfcRevolvedAreaSolidTapered shall be supported.

NOTE  View definitions and implementer agreements can further constrain the allowed swept solid types.

• Profile: see 'SweptSolid' geometric representation
• Extrusion: not applicable

The following constraints apply to the 'Clipping' representation:

• Solid: see 'SweptSolid' geometric representation
• Profile: see 'SweptSolid' geometric representation
• Extrusion: see 'SweptSolid' geometric representation
• Boolean result: The IfcBooleanClippingResult shall be supported, allowing for Boolean differences between the swept solid (here IfcExtrudedAreaSolid) and one or several IfcHalfSpaceSolid.

Figure 1 illustrates a 'Clipping' geometric representation with use of IfcBooleanClippingResult between an IfcExtrudedAreaSolid and an IfcHalfSpaceSolid to create a clipped body.

Figure 1 — Column clipping

The IfcColumnStandardCase defines in addition that the IfcColumnType should have a unique IfcMaterialProfileSet, that is referenced by the IfcMaterialProfileSetUsage assigned to all occurrences of this IfcColumnType. Composite profile columns can be represented by refering to several IfcMaterialProfile's within the IfcMaterialProfileSet that is referenced from the IfcMaterialProfileSetUsage.

Figure 1 illustrates assignment of IfcMaterialProfileSetUsage and IfcMaterialProfileSet to the IfcColumnStandardCase as the column occurrence and to the IfcColumnType. The same IfcMaterialProfileSet shall be shared by many occurrences of IfcMaterialProfileSetUsage. This relationship shall be consistent to the relationship between the IfcColumnType and the IfcColumnStandardCase.

Figure 1 — Column profile usage

Figure 2 illustrates cardinal point alignment.

NOTE  It has to be guaranteed that the use of IfcCardinalPointEnum is consistent to the placement of the extrusion body provided by IfcExtrudedAreaSolid.Position

NOTE  The cardinal points 7 (top left), and 6 (mid-depth right) are assigned according to the definition at IfcCardinalPointReference

Figure 2 — Column cardinal points

Figure 3 illustrates assignment of a composite profile by using IfcCompositeProfile for geometric representation and several IfcMaterialProfile's within the IfcMaterialProfileSet. The number of IfcMaterialProfile's within the IfcMaterialProfileSet is restricted to maximal 2 and requires the use of IfcExtrudedAreaSolidTapered, or IfcRevolvedAreaSolidTapered for the correct 'Body' shape representation.

Figure 3 — Column composite profiles

The following restriction is imposed:

• The local placement shall provide the location and directions for the standard column, the x/y plane is the plane for the start profile, and the z-axis is the extrusion axis for the column body (in case of rotation, the tangent direction).

The following additional constraints apply to the 'Axis' representation, if the 'Body' shape representation has the RepresentationType : 'SweptSolid':

• Axis
  • IfcPolyline having two Points, or IfcTrimmedCurve with BasisCurve of Type IfcLine for 'SweptSolid' provided as IfcExtrudedAreaSolid. The axis curve lies on the z axis of the object coordinate system.
  • IfcTrimmedCurve with BasisCurve of Type IfcCircle for 'SweptSolid' provided as IfcRevolvedAreaSolid. The axis curve lies on the x/z plane of the object coordinate system, the tangent at the start is along the positive z-axis.

	EXAMPLE  As shown in Figure 1, the axis shall be defined along the z axis of the object coordinate system. The axis representation can be used to represent the system length of a column that may extent the body length of the column.
Figure 1 — Column axis representation

EXAMPLE  As shown in Figure 2, the axis representation shall be used to represent the cardinal point as the offset between the 'Axis' and the extrusion path of the column. The extrusion path is provided as IfcExtrudedAreaSolid.ExtrudedDirection and should be parallel to the 'Axis'. It has to be guaranteed that the value provided by IfcMaterialProfileSetUsage.CardinalPoint is consistent to the IfcExtrudedAreaSolid.Position.

Figure 2 — Column axis cardinal point

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

• Solid: IfcExtrudedAreaSolid, IfcRevolvedAreaSolid shall be supported
• Profile: all subtypes of IfcProfileDef (with exception of IfcArbitraryOpenProfileDef)
• Profile Position : For all single profiles, the IfcParameterizedProfileDef.Position shall be NIL, or having Location = 0.,0. and RefDirection = 1.,0.
• Extrusion: perpendicular to the profile direction. The IfcExtrudedAreaSolid.ExtrudedDirection shall be [0.,0.,1.].
• Orientation: The y-axis of the profile, as determined by IfcSweptAreaSolid.Position.P[2] shall point to the Y-Axis. It indicates the "role" of the column, a role=0° means y-axis of profile = Y-axis of reference coordinate system.

Figure 1 illustrates a standard geometric representation with cardinal point applied as 5 (mid-depth centre).

The following interpretation of dimension parameter applies for rectangular columns:

• IfcRectangleProfileDef.YDim interpreted as column width
• IfcRectangleProfileDef.XDim interpreted as column depth

The following interpretation of dimension parameter applies for circular columns:

• IfcCircleProfileDef.Radius interpreted as column radius.

Figure 1 — Column body extrusion

The following additional constraints apply to the 'AdvancedSweptSolid' representation type:

• Solid: IfcSurfaceCurveSweptAreaSolid, IfcFixedReferenceSweptAreaSolid, IfcExtrudedAreaSolidTapered, IfcRevolvedAreaSolidTapered shall be supported.

NOTE  View definitions and implementer agreement can further constrain the allowed swept solid types.

• Profile: see 'SweptSolid' geometric representation
• Profile Position : see 'SweptSolid' geometric representation
• Extrusion: not applicable

The following constraints apply to the 'Clipping' representation:

• Solid: see 'SweptSolid' geometric representation
• Profile: see 'SweptSolid' geometric representation
• Profile Position : see 'SweptSolid' geometric representation
• Extrusion: see 'SweptSolid' geometric representation
• Orientation: see 'SweptSolid' geometric representation
• Boolean result: The IfcBooleanClippingResult shall be supported, allowing for Boolean differences between the swept solid (here IfcExtrudedAreaSolid) and one or several IfcHalfSpaceSolid (or its subtypes).

Figure 1 illustrates a 'Clipping' geometric representation with use of IfcBooleanClippingResult between an IfcExtrudedAreaSolid and an IfcHalfSpaceSolid to create a clipped body, with cardinal point applied as 2 (bottom centre).

Figure 1 — Column body clipping

The material of the IfcColumnType is defined by the IfcMaterialProfileSet or as fall back by IfcMaterial and attached by the IfcRelAssociatesMaterial.RelatingMaterial. It is accessible by the inverse HasAssociations relationship.

NOTE  It is illegal to assign an IfcMaterial to an IfcColumnType, if there is at least one occurrences of IfcColumnStandardCase for this type.

The shared profile definition is defined by assigning an IfcMaterialProfileSet (see material use definition above). The IfcMaterialProfile refers to the subtype of IfcProfileDef that is the common profile for all column occurrence, if used. It is only applicable if the IfcColumnType has only occurrences of type IfcColumnStandardCase (see definition of IfcColumnStandardCase for further information).

NOTE  The attribute ProfileName of the IfcProfileDef subtype, referenced in IfcMaterialProfile should contain a standardized profile name according to local standards. However, an additional geometric representation of the profile is necessary (e.g. as IfcExtrudedAreaSolid). An importing application is allowed to check for the existence of the profile name: in case of identifying it as a standardized name, the corresponding profile geometry and possibly other cross sectional properties can be read from a library. Otherwise the geometric representation and possible non geometric IfcProfileProperties have to be used.

The IfcColumnType may define the shared geometric representation for all column occurrences. The RepresentationMaps attribute refers to a list of IfcRepresentationMap's, that allow for multiple geometric representations (e.g. with IfcShapeRepresentation's having an RepresentationIdentifier 'Box', 'Axis', or 'Body'). It is only applicable if the IfcColumnType has only occurrences of type IfcColumn (See geometric use definition of IfcColumn for further information).

NOTE  If the IfcColumnType has an associated IfcMaterialProfileSet, then no shared geometric representation shall be provided.

NOTE  The product shape representations are defined as RepresentationMaps (attribute of the supertype IfcTypeProduct), which get assigned by an element occurrence instance through the IfcShapeRepresentation.Item[n] being an IfcMappedItem. See IfcTypeProduct for further information.

NOTE  The values of attributes RepresentationIdentifier and RepresentationType of IfcShapeRepresentation are restricted in the same way as those for IfcColumn and IfcColumnStandardCase

Documents may be published for work plans consisting of schedules, calendars, tasks, and resources. The relationship IfcRelAssociatesDocument may be used to preserve mappings to such document where RelatingDocument points to an IfcDocumentReference and RelatedObjects includes the IfcConstructionResource as shown in Figure 184. IfcDocumentReference.ItemReference identifies the resource within the scope of the document, such as an integer or guid. The IfcDocumentReference.ReferencedDocument corresponds to the document which is uniquely identified by IfcDocumentInformation.DocumentId and/or IfcDocumentInformation.PublicationLocation. Such document mapping allows items in the document to be updated from the building information model and vice-versa.

Figure 1 — Construction resource document use

Constraints may be applied to a resource to indicate fixed work (such as total person-hours) or fixed usage (such as simultaneous workers).

The resource type may provide shared productivity and cost information, allowing tasks and resources to be selected according to lowest cost and/or shortest duration. Given an IfcProduct of a particular IfcTypeProduct type, an IfcTypeProcess may be selected from those assigned to the product type using IfcRelAssignsToProduct, and an IfcTypeResource may be selected from those assigned to the process type using IfcRelAssignsToProcess. Then IfcTask and IfcConstructionResource occurrences may be instantiated from the type definitions, applying productivitity and rate information to assigned quantities to calculate ResourceTime.ScheduleWork. Task durations can then be calculated by dividing ResourceTime.ScheduleWork by ResourceTime.ScheduleUsage.

Figure 1 — Construction resource type use

For time series properties as shown in Figure 180, each IfcTimeSeriesValue indicates a LIST of values, where the sequence of the value corresponds to the IfcCostValue at IfcConstructionResource.CostRatesConsumed. For example, if CostRatesConsumed has two IfcCostValue items in the LIST, "Standard" and "Overtime", then IfcTimeSeriesValue(IfcDuration('T8H0M0S'),IfcDuration('T2H0M0S')) would indicate 8 hours at Standard rate and 2 hours at Overtime rate. If the list of values at IfcTimeSeriesValue.ListValues is less than the size of CostRatesConsumed, then subsequent values are considered to be zero.

Figure 1 — Construction resource time series use

Resources may be decomposed into allocation pools using the IfcRelNests relationship as shown in Figure 181. For example, an IfcLaborResource for "Electrician" may be decomposed into three task-specific IfcLaborResource objects: "Electrical Rough-in", "First Floor Circuits", and "Second Floor Circuits". Both relating and related sides may represent the same ResourceTime.ScheduleUsage quantity (for example, 6 workers time-shared), or the related side may break out ResourceTime.ScheduleUsage quantities for reserved use (for example, 4 workers and 2 workers).

A common scenario is two nesting levels where the first-level resources have no task assignments; while second-level resources have specific task assignments indicating that the resource is subdivided into allocations for specific tasks. While the model allows unlimited nesting of resources, implementer agreements may restrict to two nesting levels with task assignments specifically at the second level.

Figure 1 — Construction resource composition use

Controls have assignments from products, processes, or other objects by using the relationship object IfcRelAssignsToControl.

Figure 1 illustrates controller composition use.

Figure 1 — Controller composition use

Instances of IfcCostItem are used for cost estimates, budgets, and other forms, where a variety of identification codes are used extensively to identify the meaning of the cost. Examples include project phase codes, CSI codes, takeoff sequence numbers, and cost accounts. The model allows for all classes that are ultimately subtypes of IfcObject to inherit the ability to have one or more instances of IfcClassificationReference to be assigned. Where identification codes are required, the generic IfcRelAssociatesClassification facility should be used.

An IfcCostItem can nest other instances of IfcCostItem through its relationships to IfcRelNests. This can be used to enable the development of complex groups of costs as may be found in cost schedules through to pages, sections and complete cost schedules.

There is always a summary cost item as the root item of the tree representing the cost item nesting. Subsequent instances of IfcCostItem are assigned to the summary cost item using IfcRelNests. The summary cost item itself is assigned to IfcCostSchedule through the IfcRelAssignsToControl relationship.

Figure 1 illustrates a cost item composition used for a cost schedule. Each line item has a quantity and separate unit costs where IfcCostValue.CostType indicates the category of cost. The summary item has a hierarchy of costs calculated according to IfcAppliedValueRelationship.ArithmeticOperator, where IfcCostValue.CostType identifies the category to be totalled. The Tax component has IfcCostValue.CostType set to 'Material' which indicates it is the sum of all nested values of the 'Material' category ($3 x 3000 + $118 x 100 = $20800). The Subtotal component has IfcCostValue.CostType set to an asterisk ('*') which indicates it is the sum of all nested values of all categories.

Figure 1 — Cost composition

An IfcCostItem can be calculated based on quantities from objects through its relationship to IfcRelAssignsToControl.

For quantity-based costing, IfcElement, IfcTask, or IfcResource occurrence subtypes may be used. Multiple elements may be assigned of the same or different types, using IfcPhysicalQuantity entities defined at each object. Each IfcPhysicalQuantity type must be identical (for example, all values are IfcAreaQuantity) such that they can be added together.

For rate-based costing (specifically for IfcCostScheduleTypeEnum.SCHEDULEOFRATES), a single IfcTypeProduct, IfcTypeProcess, or IfcTypeResource subtype may be used to reflect rates for occurrences of such types. This enables the possibility to generate a quantity-based cost schedule for occurrences based on types with rate-based cost schedules.

IfcRelAssignsToControl is also used in the opposite direction to link the root IfcCostItem to an IfcCostSchedule where RelatingControl is the IfcCostSchedule.

Figure 1 illustrates cost item assignment derived from building elements. The IfcRelAssignsToControl relationship indicates building elements for which quantities are derived. Not shown, costs may also be derived from building elements by traversing assignment relationships from the assigned IfcProduct to IfcProcess to IfcResource, where all costs ultimately originate at resources. It is also possible for cost items to have assignments from processes or resources directly.

Figure 1 — Cost assignment

Approvals may be associated to indicate the status of acceptance or rejection using the IfcRelAssociatesApproval relationship where RelatingApproval refers to an IfcApproval and RelatedObjects contains the IfcCostSchedule. Approvals may be split into sub-approvals using IfcApprovalRelationship to track approval status separately for each party where RelatingApproval refers to the higher-level approval and RelatedApprovals contains one or more lower-level approvals. The hierarchy of approvals implies sequencing such that a higher-level approval is not executed until all of its lower-level approvals have been accepted.

The IfcCostSchedule may be assigned to the following entities using relationships as indicated:

• IfcActor (IfcRelAssignsToActor): Persons and organizations involved in the preparation, submittal, and as target users.

The IfcCostSchedule may have assignments of its own using the IfcRelAssignsToControl relationship where RelatingControl refers to the IfcCostSchedule and RelatedObjects contains one or more objects of the following types:

• IfcCostItem: Indicates costs published within this cost schedule, typically a single root cost item forming a hierarchy of nested cost items.

The IfcCovering has a containment relationship within the hierarchical spatial structure.

• The IfcCovering is places within the project spatial hierarchy using the objectified relationship IfcRelContainedInSpatialStructure, referring to it by its inverse attribute SELF\IfcElement.ContainedInStructure. Subtypes of IfcSpatialStructureElement are valid spatial containers, with IfcSpace being the default container.

Coverings for surfaces (CEILING, FLOORING, CLADDING, CEILING, ROOFING) may have materials defined according to layers.

Coverings for edges (MOLDING, SKIRTINGBOARD) may have materials defined according to profiles.

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  Figure 1 illustrates a planar surface representation where the area of IfcCovering is given by an IfcPolyLoop for planar base surfaces (here provided by the IfcRelSpaceBoundary). The implicit planar surface of the IfcPolyLoop shall be identical with the planar surface defined by the IfcRelSpaceBoundary.
Figure 1 — Covering surface planar

EXAMPLE  Figure 2 illustrates a cylindrical surface representation where the area of the IfcCovering is given by an IfcSurfaceOfLinearExtrusion for cylindrical base surfaces (here given by the IfcRelSpaceBoundary, such as caused by a round wall). The geometry representation of the IfcCovering is given by the IfcTrimmedCurved (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.

Figure 2 — Covering surface cylindrical

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  Figure 1 illustrates a body representation where 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.
Figure 1 — Covering body planar

EXAMPLE  Figure 2 illustrates a body representation where the volume of the IfcCovering is given by an IfcExtrudedAreaSolid for cylindrical base surfaces (here given by the IfcRelSpaceBoundary - such as 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.

Figure 2 — Covering body circular

The material of the IfcCoveringType is defined by IfcMaterialLayerSet for layer-based coverings or as fall back by IfcMaterial and attached by the IfcRelAssociatesMaterial.RelatingMaterial. It is accessible by the inverse HasAssociations relationship.

The material of the IfcCoveringType is defined by IfcMaterialProfileSet for profile-based coverings or as fall back by IfcMaterial and attached by the IfcRelAssociatesMaterial.RelatingMaterial. It is accessible by the inverse HasAssociations relationship.

The IfcCoveringType may define the shared geometric representation for all covering occurrences. The RepresentationMaps attribute refers to a list of IfcRepresentationMap's, that allow for multiple geometric representations (e.g. with IfcShaperepresentation's having an RepresentationIdentifier 'Box', 'Surface', or 'Body'). (See geometric use definition of IfcCovering for further information).

NOTE  If the IfcCoveringType has an associated IfcMaterialLayerSet, then no shared geometric representation shall be provided.

NOTE  The product shape representations are defined as RepresentationMaps (attribute of the supertype IfcTypeProduct), which get assigned by an element occurrence instance through the IfcShapeRepresentation.Item[n] being an IfcMappedItem. See IfcTypeProduct for further information.

NOTE  The values of attributes RepresentationIdentifier and RepresentationType of IfcShapeRepresentation are restricted in the same way as those for IfcCoveringType.

The following restriction may be imposed by view definitions or implementer agreements:

• If the IfcCurtainWall establishes an aggregate, then all contained elements shall be placed relative to the IfcCurtainWall.ObjectPlacement.

The following additional constraints apply to the 'Axis' representation:

• Geometry : IfcPolyline having two Points, or IfcTrimmedCurve with BasisCurve of type IfcLine or IfcCircle.

The material of the IfcDistributionChamberElement is defined by IfcMaterialConstituentSet or as a fallback by IfcMaterial, and attached by the RelatingMaterial attribute on the IfcRelAssociatesMaterial relationship. It is accessible by the HasAssociations inverse attribute. Material information can also be given at the IfcDistributionChamberElementType, defining the common attribute data for all occurrences of the same type. The following keywords for IfcMaterialConstituentSet.MaterialConstituents[n].Name shall be used:

• 'Base': The material from which the base of the duct is constructed.
• 'Cover': The material from which the access cover to the chamber is constructed.
• 'Fill': The material that is used to fill the duct (where used).
• 'Wall': The material from which the wall of the duct is constructed.

In addition to general product and project classification (UniFormat, etc.), classifications may also be applied to indicate a device address or addressing scheme according to system-based device instance classification.

Figure 1 illustrates classification usage.

Figure 1 — Distribution control classification

The IfcDistributionControlElement may be assigned to the following entities using relationships as indicated:

• IfcDistributionSystem (IfcRelAssignsToGroup): Indicates a system containing interconnected devices, where control elements are typically part of a control system having PredefinedType=CONTROL.
• IfcPerformanceHistory (IfcRelAssignsToControl): Indicates realtime or historical infomation captured for the device.

The IfcDistributionElement defines the occurrence of any HVAC, electrical, sanitary or other element within a distribution system. Common information about distribution element types (or styles) is handled by subtypes of IfcDistributionElementType. The IfcDistributionElementType (if present) may establish the common type name, usage (or predefined) type, common material, common set of properties and common shape representations (using IfcRepresentationMap). The IfcDistributionElementType is attached using the IfcRelDefinedByType.RelatingType objectified relationship and is accessible by the inverse IsDefinedBy attribute.

The assignment of types to distribution element occurrences is vital for providing the additional meaning, or ontology, of the distribution element. Many specialized type are defined in other schemas of this specification.

The quantities relating to the IfcDistributionElement are defined by the IfcElementQuantity and attached by the IfcRelDefinesByProperties. A detailed specification for individual quantities is introduced at the level of subtypes of IfcDistributionElement.

The IfcDistributionElement may be contained within the spatial containment tree. The IfcSpace is the default spatial container.

NOTE  The 'Spatial Containment' concept is mandatory in many model view definitions.

This represents the 3D flow path of the item having IfcShapeRepresentation.RepresentationType of 'Curve3D' and containing a single IfcBoundedCurve subtype such as IfcPolyline, IfcTrimmedCurve, or IfcCompositeCurve. For elements containing directional ports (IfcDistributionPort with FlowDirection of SOURCE or SINK), the direction of the curve indicates direction of flow where a SINK port is positioned at the start of the curve and a SOURCE port is positioned at the end of the curve. This representation is most applicable to flow segments (pipes, ducts, cables), however may be used at other elements to define a primary flow path if applicable.

This represents the 3D clearance volume of the item having RepresentationType of 'Surface3D'. Such clearance region indicates space that should not intersect with the 'Body' representation of other elements, though may intersect with the 'Clearance' representation of other elements. The particular use of clearance space may be for safety, maintenance, or other purposes.

This represents the 3D flow path of the item having IfcShapeRepresentation.RepresentationType of 'Curve3D' and containing a single IfcBoundedCurve subtype such as IfcPolyline, IfcTrimmedCurve, or IfcCompositeCurve. For elements containing directional ports (IfcDistributionPort with FlowDirection of SOURCE or SINK), the direction of the curve indicates direction of flow where a SINK port is positioned at the start of the curve and a SOURCE port is positioned at the end of the curve. This representation is most applicable to flow segment types (pipes, ducts, cables), however may be used at other elements to define a primary flow path if applicable.

If an element type is defined parametrically (such as a flow segment type defining common material profile but no particular length or path), then no representations shall be asserted at the type.

NOTE  The product representations are defined as representation maps (at the level of the supertype IfcTypeProduct, which get assigned by an element occurrence instance through the IfcShapeRepresentation.Item[1] being an IfcMappedItem.

This represents the 3D clearance volume of the item having RepresentationType of 'Surface3D'. Such clearance region indicates space that should not intersect with the 'Body' representation between element occurrences, though may intersect with the 'Clearance' representation of other element occurrences. The particular use of clearance space may be for safety, maintenance, or other purposes.

This represents the light emission of the item having IfcShapeRepresentation.RepresentationType of 'LightSource' and containing one or more IfcLightSource subtypes. This representation is most applicable to lamps and light fixtures, however may be used at other elements that emit light.

The placement of a port indicates the position and orientation of how it may connect to a compatible port on another product. The placement shall be relative to the nesting IfcDistributionElement, IfcDistributionElementType, or enclosing IfcDistributionPort.

The Location is the midpoint of the physical connection, unless otherwise indicated by cardinal point on a material profile.

The Axis points in the direction of the physical connection away from the product if FlowDirection equals SOURCE (or SOURCEANDSINK or NOTDEFINED), or points opposite direction (to the product) if the FlowDirection equals SINK.

NOTE  The rationale for positioning the Axis in the direction of flow is to allow for the same geometry to be used, such as for connectors with polarized cross-section.

The RefDirection points in the direction of the local X axis of the material profile, where the local Y axis points up if looking towards the Axis where the local X axis points right.

Upon connecting elements through ports with rigid connections, each object shall be aligned such that the effective Location, Axis, and RefDirection of each port is aligned to be equal (with exception for circular profiles where the RefDirection need not be equal).

Distribution ports are indicated on products and product types using the IfcRelNests relationship where RelatingObject refers to the enclosing IfcDistributionElement or IfcDistributionElementType respectively. The order of ports indicates logical ordering such within outlets, junction boxes, or communications equipment.

Ports may be further nested into sub-ports, for indicating specific connections on components or pins.

IfcDistributionPort may be connected to other objects as follows using the indicated relationship:

• IfcDistributionPort (IfcRelConnectsPorts) : Indicates a connection to another port having the same type and opposite flow direction. For port connections between elements, the RelatingPort is set to a port having FlowDirection=SOURCE and the RelatedPort is set to a port having FlowDirection=SINK. For aggregation scenarios, ports on a device may be mapped to aggregated devices within, in which case ports on the outer device indicate a single FlowDirection but have an additional connection internally to a port on an aggregated inner device. Refer to IfcUnitaryEquipment for an example.
• IfcDistributionElement (through IfcRelConnectsPortToElement): For dynamic ports, indicates the containing element.

Figure 1 illustrates distribution port connectivity.

Figure 1 — Distribution port connectivity

The IfcDistributionPort may be assigned to the following entities using relationships as indicated:

• IfcDistributionSystem (through IfcRelAssignsToGroup): Indicates a system containing interconnected devices.
• IfcPerformanceHistory< (through IfcRelAssignsToControl): Indicates real time or historical infomation captured for the device.

For the most common case of an IfcDistributionElement subtype containing ports of a particular PredefinedType that all belong to the same distribution system, the IfcDistributionElement is assigned to the IfcDistributionSystem via the IfcRelAssignsToGroup relationship, where IfcDistributionPort's are implied as part of the corresponding system based on their PredefinedType. An IfcDistributionElement may belong to multiple systems, however only one IfcDistributionSystem of a particular PredefinedType.

For rare cases where an IfcDistributionElement subtype contains ports of the same PredefinedType yet different ports belong to different systems, alternatively each IfcDistributionPort may be directly assigned to a single IfcDistributionSystem via the IfcRelAssignsToGroup relationship, where the PredefinedType must match. Such assignment indicates that the IfcDistributionSystem assigned from the IfcDistributionPort overrides any such system of the same PredefinedType assigned from the containing IfcDistributionElement, if any.

Additionally, an IfcDistributionSystem may in turn be assigned to an IfcDistributionPort indicating the host or origination of the system using IfcRelAssignsToProduct.

EXAMPLE  A gas-powered hot water heater may have three ports: GAS, DOMESTICCOLDWATER, and DOMESTICHOTWATER. The heater is a member of two systems (GAS and DOMESTICCOLDWATER), and hosts one system (DOMESTICHOTWATER) at the corresponding port.

Figure 1 illustrates a distribution system for an electrical circuit.

Figure 1 — Distribution system assignment

The opening direction is determined by the local placement of IfcDoor and the OperationType of the IfcDoorType as shown in Figure 1.

NOTE  There are different definitions in various countries on what a left opening or left hung or left swing door is (same for right). Therefore the IFC definition may derivate from the local standard and need to be mapped appropriately.

Opening directions Definitions Reference to other standards The door panel (for swinging doors) opens always into the direction of the positive Y axis of the local placement. The determination of whether the door opens to the left or to the right is done at the level of the IfcDoorType. Here it is a left side opening door given by IfcDoorType.OperationType = SingleSwingLeft refered to as LEFT HAND (LH) in US * refered to as DIN-R (right hung) in Germany If the door should open to the other side, then the local placement has to be changed. It is still a left side opening door, given by IfcDoorType.OperationType = SingleSwingLeft refered to as RIGHT HAND REVERSE (RHR) in US * refered to as DIN-R (right hung) in Germany If the door panel (for swinging doors) opens to the right, a separate door style needs to be used (here IfcDoorTypee.OperationType = SingleSwingRight) and it always opens into the direction of the positive Y axis of the local placement. refered to as RIGHT HAND (RH) in US * refered to as DIN-L (left hung) in Germany If the door panel (for swinging doors) opens to the right, and into the opposite directions, the local placement of the door need to change. The door style is given by IfcDoorType.OperationType = SingleSwingRight. refered to as LEFT HAND REVERSE (LHR) in US * refered to as DIN-L (left hung) in Germany * it assumes that the 'inside/private/primary' space is above (top in the pictures) and the 'outside/public/secondary' space is below (bottom in the pictures).

Figure 1 — Door swing

NOTE  The OverallWidth and OverallHeight parameters are for informational purpose only.

The material of the IfcDoor is defined by the IfcMaterialConstituentSet or as fall back by IfcMaterial and attached by the IfcRelAssociatesMaterial relationship.

The following restriction is imposed:

1. The PlacementRelTo relationship of IfcLocalPlacement shall point to the local placement of the same element (if given), in which the IfcDoor is used as a filling (normally an IfcOpeningElement), as provided by the IfcRelFillsElement relationship;
2. If the IfcDoor is part of an assembly, e.g. an IfcCurtainWall, then the PlacementRelTo relationship of IfcLocalPlacement shall point (if given) to the local placement of that assembly;
3. If the IfcDoor is not inserted into an IfcOpeningElement, then the PlacementRelTo relationship of IfcLocalPlacement shall point (if given) to the local placement of the same IfcSpatialStructureElement that is used in the ContainedInStructure inverse attribute or to a referenced spatial structure element at a higher level.

NOTE  The product placement is used to determine the opening direction of the door.

The door profile is represented by a three-dimensional closed curve within a particular shape representation. The profile is used to apply the parameter of the parametric door representation. Only a single closed curve shall be contained in the set of IfcShapeRepresentation.Items.

A 'Profile' representation has to be provided if a parametric representation is applied to the door.

The IfcDoor, as any subtype of IfcBuildingElement, may participate alternatively in one of the two different containment relationships:

• the Spatial Containment (defined here), or
• the Element Composition.

The IfcDoor may also be connected to the IfcOpeningElement in which it is placed as a filler. In this case, the spatial containment relationship shall be provided, see Figure 1.

	NOTE  The containment shall be defined independently of the filling relationship, that is, even if the IfcDoor is a filling of an opening established by IfcRelFillsElement, it is also contained in the spatial structure by IfcRelContainedInSpatialStructure.
Figure 1 — Door spatial containment

The door profile is represented by a three-dimensional closed curve within a particular shape representation. The profile is used to apply the parameter of the parametric door representation. The following attribute values for the IfcShapeRepresentation holding this geometric representation shall be used:

• RepresentationIdentifier : 'Profile'
• RepresentationType : 'Curve3D' or 'GeometricCurveSet', in case of 'GeometricCurveSet' only a single closed curve shall be contained in the set of IfcShapeRepresentation.Items.

The following additional constraints apply to the 'Profile' representation type:

• Curve: being an IfcPolyline defining a rectangle.
• Position: The curve shall lie in the xz plane of the object placement coordinate (the y coordinate values of the IfcCartesianPoint's shall be 0.).

EXAMPLE  Figure 1 illustrates applying the door lining parameters to the door profile shape representation. The profile defines the outer boundary to which the door lining parameters relate as: <li class="small"><em>IfcDoorLiningProperties.LiningDepth</em> starting at distance defined by LiningOffset going into the positive y direction. <li class="small"><em>IfcDoorLiningProperties.LiningThickness</em> offset into the inner side of the rectangle. IfcDoorLiningProperties.LiningOffset distance along the positive y direction to where the LiningDepth applies. IfcDoorLiningProperties.ThresholdThickness starting at the bottom edge of the rectangle into the inner side of the rectangle <li class="small"><em>IfcDoorLiningProperties.ThresholdDepth</em> starting at distance defined by LiningOffset going into the positive y direction. <li class="small"><em>IfcDoorLiningProperties.TransomOffset</em> starting at the bottom edge of the rectangle (along local x axis) into the inner side of the rectangle, distance provided as percentage of overall height. Distance to the centre line of the transom.

Figure 1 — Door profile

Two subtypes of IfcPreDefinedPropertySet are applicable to IfcDoorType:

• IfcDoorLiningProperties - a single instance to define the shape parameters of the door lining
• IfcDoorPanelProperties - one or several instances to define the shape parameters of the door panel(s)

The object placement for any subtype of IfcElement is defined by the IfcObjectPlacement, either IfcLocalPlacement or IfcGridPlacement, which defines the local object coordinate system that is referenced by all geometric representations of that IfcElement.

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.

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.

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.

	EXAMPLE  As shown in Figure 1, 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 1 — Element surface model representation

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.

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.

	EXAMPLE  As shown in Figure 1, 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 1 — Building element body boundary representation

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.

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.

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.

The IfcElementAssembly shall represent an aggregate, i.e. it should have other elements, being subtypes of IfcElement, as contained (sub)parts. The table above only represents a selection of subtypes of IfcElement that are legitimate as parts in an IfcElementAssembly

• The IfcElementAssembly is an aggregate i.e. being composed by other elements and acting as an assembly using the objectified relationship IfcRelAggregates, refering to it by its inverse attribute SELF\IfcObjectDefinition.IsDecomposedBy. Components of an assembly are described by instances of subtypes of IfcElement.
• In this case, the contained subtypes of IfcElement shall not be additionally contained in the project spatial hierarchy, i.e. the inverse attribute SELF\IfcElement.ContainedInStructure of those IfcElement's shall be NIL.

Figure 1 illustrates spatial containment and element aggregation relationships.

Figure 1 — Element assembly containment

The IfcElementAssembly should have a relationship for its containment in the hierachical spatial structure of the project. Only if the IfcElementAssembly is itself a part of another assembly this relationship should be omitted.

The mapped item, IfcMappedItem, should be used if appropriate as it allows for reusing the geometry definition of a type at all occurrences of the same type.

A single instance of a subtype of IfcElementComponent can stand for several actual element components at once. In this case, the IfcShapeRepresentation contains as many mapped items as there are element components combined within this occurrence object.

	EXAMPLE  Figure 1 illustrates multiple components modeled as a single occurrence object (here: IfcFastener)
Figure 1 — Element component mapped representation

Representation identifier and type are the same as in single mapped representation. The number of mapped items in the representation corresponds with the count of element components in the IfcElementQuantity.

The IfcEvent defines the anticipated or actual occurrence of any event; common information about event types is handled by IfcEventType.

IfcEvent may be contained within an IfcTask using the IfcRelNests relationship. The event is considered active during the time period of the enclosing task (including any assigned IfcWorkCalendar); that is such event may be triggered within the task time period but not outside of it. As an IfcEvent is considered to be atomic, no use is anticipated for nesting processes inside the event.

The relationship IfcRelSequence is used to indicate control flow. An IfcEvent as a predecessor (IfcRelSequence.RelatingProcess) indicates that the succeeding process (typically IfcProcedure or IfcTask) is triggered in response to the event. An IfcEvent as a successor (IfcRelSequence.RelatedProcess) indicates that the completion of the preceeding process causes the event to be triggered. As events have zero duration, the IfcRelSequence.SequenceType attribute has no effect on an IfcEvent but still applies to the opposite end of the relationship if IfcTask is used.

An IfcEvent may be assigned to an IfcWorkCalendar to indicate times when such event is active using IfcRelAssignsToControl; otherwise the effective calendar is determined by the nearest IfcProcess ancestor with a calendar assigned.

For building operation scenarios, IfcEvent may be assigned to a product (IfcElement subtype) using IfcRelAssignsToProduct to indicate a specific product occurrence that sources the event.

EXAMPLE  An IfcSensor for a motion sensor may have a "Motion Sensed" event. If the IfcEvent is defined by an IfcEventType and the IfcEventType is assigned to a product type (using IfcRelAssignsToProduct), then the IfcEvent must be assigned to one or more occurrences of the specified product type using IfcRelAssignsToProduct.

NOTE  By using the inverse relationship IfcFacility.Decomposes it references IfcProject || IfcSite || IfcFacility through IfcRelAggregates.RelatingObject. If it refers to another instance of IfcFacility, the referenced IfcFacility needs to have a different and higher CompositionType, i.e. COMPLEX (if the other IfcBuilding has ELEMENT), or ELEMENT (if the other IfcFacility has PARTIAL).

NOTE  By using the inverse relationship IfcFacility.IsDecomposedBy it references IfcFacility || IfcFacilityPart through IfcRelAggregates.RelatedObjects. If it refers to another instance of IfcFacility, the referenced IfcFacility needs to have a different and lower CompositionType, i.e. ELEMENT (if the other IfcFacility has COMPLEX), or PARTIAL (if the other IfcFacility has ELEMENT).

NOTE  If there are building elements and/or other elements directly related to the IfcFacility (like a curtain wall spanning several stories), they are associated with the IfcFacility by using the objectified relationship IfcRelContainedInSpatialStructure. The IfcFacility references them by its inverse relationship: > * IfcFacility.ContainsElements -- referencing any subtype of IfcProduct (with the exception of other spatial structure element) by IfcRelContainedInSpatialStructure.RelatedElements.

The placement for IfcFacility is defined in its supertype IfcProduct. It is defined by either IfcLocalPlacement or by IfcLinearPlacement>/em> which define the local coordinate system that is referenced by all geometric representations.

• The PlacementRelTo relationship of IfcObjectPlacement shall point (if relative placement is used) to the IfcSpatialStructureElement of type IfcSite, or of type IfcFacility (e.g. to position a facility relative to a facility complex, or a facility section to a facility).
• If the relative placement is not used, the absolute placement is defined within the world coordinate system.

The body (or solid model) geometric representation (if the facility has an independent geometric representation) of IfcFacility is defined using faceted B-Rep capabilities (with or without voids), based on the IfcFacetedBrep or on the IfcFacetedBrepWithVoids. In the case of alignment based infrastructure, the geometric representation can be defined using IfcSectionedSolidHorizontal optionally IfcSweptAreaSolid.

NOTE  Since the building shape is usually described by the exterior building elements, an independent shape representation shall only be given, if the building is exposed independently from its constituting elements and such independent geometric representation may be prohibited in model view definitions.

NOTE  By using the inverse relationship IfcFacilityPart.Decomposes it references (IfcFacility || IfcFacilityPart) through IfcRelAggregates.RelatingObject_IfcFacilityPart, the referenced IfcFacilityPart needs to have a different and higher CompositionType, i.e. COMPLEX (if the other IfcFacilityPart has ELEMENT), or ELEMENT (if the other IfcFacilityPart has PARTIAL)._

If there are building elements and/or other elements directly related to the IfcFacilityPart (like most building elements, such as walls, columns, etc.), they are associated with the IfcFacilityPart by using the objectified relationship IfcRelContainedInSpatialStructure. The IfcFacilityPart references them by its inverse relationship:

• IfcFacilityPart.ContainsElements -- referencing any subtype of IfcProduct (with the exception of other spatial structure element) by IfcRelContainedInSpatialStructure.RelatedElements.

Elements can also be referenced in an IfcFacilityPart, for example, if they span through several storeys. This is expressed by using the objectified relationship IfcRelReferencedInSpatialStructure. Systems, such as building service or electrical distribution systems, zonal systems, or structural analysis systems, relate to IfcFacilityPart by using the objectified relationship IfcRelServicesBuildings.

The local placement for IfcFacilityPart 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 or by IfcLinearPlacement which measures along a linear positioning element.

• The PlacementRelTo attribute of IfcObjectPlacement shall point (if relative placement is used) to the IfcSpatialStructureElement of type IfcFacility, or of type IfcFacilityPart (e.g. to position a facility relative to a facility part complex, or a partial facility part to a facility part).
• If the relative placement is not used, the absolute placement is defined within the world coordinate system.

The body (or solid model) geometric representation (if the facility part has an independent geometric representation) of IfcFacilityPart is defined using faceted B-Rep capabilities (with or without voids), based on the IfcFacetedBrep or on the IfcFacetedBrepWithVoids or in the case of alignment based infrastructure using IfcSectionedSolidHorizontal optionally IfcSweptAreaSolid.

NOTE  Since the facility part shape is usually described by the exterior facility elements, an independent shape representation shall only be given, if the facility part is exposed independently from its constituting elements and such independent geometric representation may be prohibited in model view definitions.

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.

The material of the IfcFlowSegment is defined using one of the following entities:

• IfcMaterialProfileSetUsage : for parametric segments, this defines the cross section and alignment to the 'Axis' representation, from which the 'Body' representation may be generated.
• IfcMaterialProfileSet : for non-parametric segments (having fixed length or path), this may define the cross section for analysis purposes, however the 'Body' representation is independently generated.
• IfcMaterialConstituentSet : for elements containing multiple materials where profiles are not applicable, this indicates materials at named parts.
• IfcMaterial : for elements comprised of a single material where profiles are not applicable, this indicates the material.

The material is attached by the RelatingMaterial attribute on the IfcRelAssociatesMaterial relationship. It is accessible by the HasAssociations inverse attribute. Material information can also be given at the IfcFlowSegmentType, defining the common attribute data for all occurrences of the same type. Standard names and material types are defined at subtypes.

Standard representations are defined at the supertype IfcDistributionFlowElement. For parametric flow segments where IfcMaterialProfileSetUsage is defined and an 'Axis' representation is defined, then the 'Body' representation may be generated using the 'SweptSolid' or 'AdvancedSweptSolid' representation types by sweeping the profile(s) along the axis.

An IfcGeographicElement might be further qualified by referencing a feature catalog as a particular classification. The feature classification is assigned using the inverse relationship HasAssociations pointing to IfcClassificationReference. The attributes should have the following meaning:

• Catalog : IfcClassification.Name
• Identity: IfcClassificationReference.Identification
• ElementName: IfcClassificationReference.Name

The IfcGroup establishes an arbitrary collection of objects through utilizing this concept.