6.1.3.35 IfcSlab

6.1.3.35.1 Semantic definition

A slab is a component of the construction that may enclose a space vertically. The slab may provide the lower support (floor) or upper construction (roof slab) in any space in a building.

Only the core or constructional part of this construction is considered to be a slab. The upper finish (flooring, roofing) and the lower finish (ceiling, suspended ceiling) are considered to be coverings. A special type of slab is the landing, described as a floor section to which one or more stair flights or ramp flights connect.

A slab may have openings, such as floor openings, or recesses. They are defined by an IfcOpeningElement attached to the slab using the inverse relationship HasOpenings pointing to IfcRelVoidsElement. Slabs with openings that have already been modeled within the enclosing geometry may use the relationship IfcRelConnectsElements to associate the IfcSlab with embedded elements such as trap doors.

There are two main representations for slab occurrences:

IfcSlab with IfcMaterialLayerSetUsage is used for all occurrences of slabs, that are prismatic and where the thickness parameter can be fully described by the IfcMaterialLayerSetUsage. These slabs are always represented geometrically by a 'SweptSolid' geometry (or by a 'Clipping' geometry based on 'SweptSolid'), if a 3D geometric representation is assigned.
IfcSlab without IfcMaterialLayerSetUsage is used for all other occurrences of slabs, particularly for slabs with changing thickness, or slabs with non planar surfaces, and slabs having only 'SweptSolid' or 'Brep' geometry, or if a more parametric representation is not intended.

6.1.3.35.2 Entity inheritance

- IfcRoot

6.1.3.35.3 Attributes

#	Attribute	Type	Description
IfcRoot (4)
1	GlobalId	IfcGloballyUniqueId	Assignment of a globally unique identifier within the entire software world.
2	OwnerHistory	OPTIONAL IfcOwnerHistory	Assignment of the information about the current ownership of that object, including owning actor, application, local identification and information captured about the recent changes of the object, NOTE Only the last modification is stored - either as addition, deletion or modification. IFC4-CHANGE The attribute has been changed to be OPTIONAL.
3	Name	OPTIONAL IfcLabel	Optional name for use by the participating software systems or users. For some subtypes of IfcRoot the insertion of the Name attribute may be required. This would be enforced by a where rule.
4	Description	OPTIONAL IfcText	Optional description, provided for exchanging informative comments.
IfcObjectDefinition (7)
	HasAssignments	SET [0:?] OF IfcRelAssigns FOR RelatedObjects	Reference to the relationship objects, that assign (by an association relationship) other subtypes of IfcObject to this object instance. Examples are the association to products, processes, controls, resources or groups.
	Nests	SET [0:1] OF IfcRelNests FOR RelatedObjects	References to the decomposition relationship being a nesting. It determines that this object definition is a part within an ordered whole/part decomposition relationship. An object occurrence or type can only be part of a single decomposition (to allow hierarchical structures only). IFC4-CHANGE The inverse attribute datatype has been added and separated from Decomposes defined at IfcObjectDefinition.
	IsNestedBy	SET [0:?] OF IfcRelNests FOR RelatingObject	References to the decomposition relationship being a nesting. It determines that this object definition is the whole within an ordered whole/part decomposition relationship. An object or object type can be nested by several other objects (occurrences or types). IFC4-CHANGE The inverse attribute datatype has been added and separated from IsDecomposedBy defined at IfcObjectDefinition.
	HasContext	SET [0:1] OF IfcRelDeclares FOR RelatedDefinitions	References to the context providing context information such as project unit or representation context. It should only be asserted for the uppermost non-spatial object. IFC4-CHANGE The inverse attribute datatype has been added.
	IsDecomposedBy	SET [0:?] OF IfcRelAggregates FOR RelatingObject	References to the decomposition relationship being an aggregation. It determines that this object definition is whole within an unordered whole/part decomposition relationship. An object definition can be aggregated by several other objects (occurrences or parts). IFC4-CHANGE The inverse attribute datatype has been changed from the supertype IfcRelDecomposes to subtype IfcRelAggregates.
	Decomposes	SET [0:1] OF IfcRelAggregates FOR RelatedObjects	References to the decomposition relationship being an aggregation. It determines that this object definition is a part within an unordered whole/part decomposition relationship. An object definition can only be part of a single decomposition (to allow hierarchical structures only). IFC4-CHANGE The inverse attribute datatype has been changed from the supertype IfcRelDecomposes to subtype IfcRelAggregates.
	HasAssociations	SET [0:?] OF IfcRelAssociates FOR RelatedObjects	Reference to the relationship objects, that associates external references or other resource definitions to the object. Examples are the association to library, documentation or classification.
IfcObject (5)
5	ObjectType	OPTIONAL IfcLabel	The type denotes a particular type that indicates the object further. The use has to be established at the level of instantiable subtypes. In particular it holds the user defined type, if the enumeration of the attribute PredefinedType is set to USERDEFINED or when the concrete entity instantiated does not have a PredefinedType attribute. The latter is the case in some exceptional leaf classes and when instantiating IfcBuiltElement directly.
	IsDeclaredBy	SET [0:1] OF IfcRelDefinesByObject FOR RelatedObjects	Link to the relationship object pointing to the declaring object that provides the object definitions for this object occurrence. The declaring object has to be part of an object type decomposition. The associated IfcObject, or its subtypes, contains the specific information (as part of a type, or style, definition), that is common to all reflected instances of the declaring IfcObject, or its subtypes. IFC4-CHANGE New inverse relationship, change made with upward compatibility for file based exchange.
	Declares	SET [0:?] OF IfcRelDefinesByObject FOR RelatingObject	Link to the relationship object pointing to the reflected object(s) that receives the object definitions. The reflected object has to be part of an object occurrence decomposition. The associated IfcObject, or its subtypes, provides the specific information (as part of a type, or style, definition), that is common to all reflected instances of the declaring IfcObject, or its subtypes. IFC4-CHANGE New inverse relationship, change made with upward compatibility for file based exchange.
	IsTypedBy	SET [0:1] OF IfcRelDefinesByType FOR RelatedObjects	Set of relationships to the object type that provides the type definitions for this object occurrence. The then associated IfcTypeObject, or its subtypes, contains the specific information (or type, or style), that is common to all instances of IfcObject, or its subtypes, referring to the same type. IFC4-CHANGE New inverse relationship, the link to IfcRelDefinesByType was previously included in the inverse relationship IfcRelDefines. Change made with upward compatibility for file based exchange.
	IsDefinedBy	SET [0:?] OF IfcRelDefinesByProperties FOR RelatedObjects	Set of relationships to property set definitions attached to this object. Those statically or dynamically defined properties contain alphanumeric information content that further defines the object. IFC4-CHANGE The data type has been changed from IfcRelDefines to IfcRelDefinesByProperties with upward compatibility for file based exchange.
IfcProduct (5)
6	ObjectPlacement	OPTIONAL IfcObjectPlacement	This establishes the object coordinate system and 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 constrained (e.g. relative to grid axes, or to a linear positioning element). The type of placement is determined by the various subtypes of IfcObjectPlacement. An object placement must be provided if a representation is present.
7	Representation	OPTIONAL IfcProductRepresentation	Reference to the representations of the product, being either a representation (IfcProductRepresentation) or as a special case of a shape representation (IfcProductDefinitionShape). The product definition shape provides for multiple geometric representations of the shape property of the object within the same object coordinate system, defined by the object placement.
	ReferencedBy	SET [0:?] OF IfcRelAssignsToProduct FOR RelatingProduct	Reference to the IfcRelAssignsToProduct relationship, by which other products, processes, controls, resources or actors (as subtypes of IfcObjectDefinition) can be related to this product.
	PositionedRelativeTo	SET [0:?] OF IfcRelPositions FOR RelatedProducts	Reference to the IfcRelPositions relationship, which defines its relationship with a positioning element.
	ReferencedInStructures	SET [0:?] OF IfcRelReferencedInSpatialStructure FOR RelatedElements	Reference to the objectified relationship IfcRelReferencedInSpatialStructure may be used to relate a product to one or more spatial structure elements in addition to the one in which it is primarily contained.
IfcElement (13)
8	Tag	OPTIONAL IfcIdentifier	The tag (or label) identifier at the particular instance of a product, e.g. the serial number, or the position number. It is the identifier at the occurrence level.
	FillsVoids	SET [0:1] OF IfcRelFillsElement FOR RelatedBuildingElement	Reference to the IfcRelFillsElement relationship that puts the element as a filling into the opening created within another element.
	ConnectedTo	SET [0:?] OF IfcRelConnectsElements FOR RelatingElement	Reference to the element connection relationship. The relationship then refers to the other element to which this element is connected to.
	IsInterferedByElements	SET [0:?] OF IfcRelInterferesElements FOR RelatedElement	Reference to the interference relationship to indicate the element that is interfered. The relationship, if provided, indicates that this element has an interference with one or many other elements. NOTE There is no indication of precedence between IsInterferedByElements and InterferesElements. IFC4-CHANGE New inverse relationship.
	InterferesElements	SET [0:?] OF IfcRelInterferesElements FOR RelatingElement	Reference to the interference relationship to indicate the element that interferes. The relationship, if provided, indicates that this element has an interference with one or many other elements. NOTE There is no indication of precedence between IsInterferedByElements and InterferesElements. IFC4-CHANGE New inverse relationship.
	HasProjections	SET [0:?] OF IfcRelProjectsElement FOR RelatingElement	Projection relationship that adds a feature (using a Boolean union) to the IfcBuiltElement.
	HasOpenings	SET [0:?] OF IfcRelVoidsElement FOR RelatingBuildingElement	Reference to the IfcRelVoidsElement relationship that creates an opening in an element. An element can incorporate zero-to-many openings. For each opening, that voids the element, a new relationship IfcRelVoidsElement is generated.
	IsConnectionRealization	SET [0:?] OF IfcRelConnectsWithRealizingElements FOR RealizingElements	Reference to the connection relationship with realizing element. The relationship, if provided, assigns this element as the realizing element to the connection, which provides the physical manifestation of the connection relationship.
	ProvidesBoundaries	SET [0:?] OF IfcRelSpaceBoundary FOR RelatedBuildingElement	Reference to space boundaries by virtue of the objectified relationship IfcRelSpaceBoundary. It defines the concept of an element bounding spaces.
	ConnectedFrom	SET [0:?] OF IfcRelConnectsElements FOR RelatedElement	Reference to the element connection relationship. The relationship then refers to the other element that is connected to this element.
	ContainedInStructure	SET [0:1] OF IfcRelContainedInSpatialStructure FOR RelatedElements	Containment relationship to the spatial structure element, to which the element is primarily associated. This containment relationship has to be hierarchical, i.e. an element may only be assigned directly to zero or one spatial structure.
	HasCoverings	SET [0:?] OF IfcRelCoversBldgElements FOR RelatingBuildingElement	Reference to IfcCovering by virtue of the objectified relationship IfcRelCoversBldgElements. It defines the concept of an element having coverings associated.
	HasSurfaceFeatures	SET [0:?] OF IfcRelAdheresToElement FOR RelatingElement	Reference to the IfcRelAdheresToElement relationship that adheres a IfcSurfaceFeature to an element. An element can incorporate zero-to-many surface features in one relationship.
Click to show 34 hidden inherited attributes
IfcSlab (1)
9	PredefinedType	OPTIONAL IfcSlabTypeEnum	Predefined generic type for a slab that is specified in an enumeration. There may be a property set given specifically for the predefined types. NOTE The PredefinedType shall only be used, if no IfcSlabType is assigned, providing its own IfcSlabType.PredefinedType. IFC2x-CHANGE The attribute has been changed into an OPTIONAL attribute.

Table 6.1.3.35.P

6.1.3.35.4 Formal propositions

Name Description

CorrectPredefinedType

Either the PredefinedType attribute is unset (e.g. because an IfcSlabType is associated), or the inherited attribute ObjectType shall be provided, if the PredefinedType is set to USERDEFINED.

 NOT(EXISTS(PredefinedType)) OR
 (PredefinedType <> IfcSlabTypeEnum.USERDEFINED) OR
 ((PredefinedType = IfcSlabTypeEnum.USERDEFINED) AND EXISTS (SELF\IfcObject.ObjectType))

CorrectTypeAssigned

Either there is no slab type object associated, i.e. the IsTypedBy inverse relationship is not provided, or the associated type object has to be of type IfcSlabType.

 (SIZEOF(IsTypedBy) = 0) OR
  ('IFC4X3_DEV_738df036.IFCSLABTYPE' IN TYPEOF(SELF\IfcObject.IsTypedBy[1].RelatingType))

Table 6.1.3.35.Q

6.1.3.35.5 Property sets

Pset_CessBetweenRails TRACKSLAB
- JointRelativePosition
- CheckRailType
- LoadCapacity
- UsagePurpose
Pset_ConcreteElementGeneral
- AssemblyPlace
- CastingMethod
- StructuralClass
- StrengthClass
- ExposureClass
- ReinforcementVolumeRatio
- ReinforcementAreaRatio
- DimensionalAccuracyClass
- ConstructionToleranceClass
- ConcreteCover
- ConcreteCoverAtMainBars
- ConcreteCoverAtLinks
- ReinforcementStrengthClass
Pset_Condition
- AssessmentDate
- AssessmentCondition
- AssessmentDescription
- AssessmentType
- AssessmentMethod
- LastAssessmentReport
- NextAssessmentDate
- AssessmentFrequency
Pset_ConstructionAdministration
- ProcurementMethod
- SpecificationSectionNumber
- SubmittalIdentifer
Pset_ConstructionOccurence
- InstallationDate
- ModelNumber
- TagNumber
- AssetIdentifier
Pset_ElementKinematics
- CyclicPath
- CyclicRange
- LinearPath
- LinearRange
- MaximumAngularVelocity
- MaximumConstantSpeed
- MinimumTime
Pset_EmbeddedTrack TRACKSLAB
- IsAccessibleByVehicle
- HasDrainage
- PermissibleRoadLoad
Pset_EnvironmentalCondition
- ReferenceAirRelativeHumidity
- ReferenceEnvironmentTemperature
- MaximumAtmosphericPressure
- StorageTemperatureRange
- MaximumWindSpeed
- OperationalTemperatureRange
- MaximumRainIntensity
- SaltMistLevel
- SeismicResistance
- SmokeLevel
- MaximumSolarRadiation
Pset_EnvironmentalImpactIndicators
- Reference
- FunctionalUnitReference
- IndicatorsUnit
- LifeCyclePhase
- ExpectedServiceLife
- TotalPrimaryEnergyConsumptionPerUnit
- WaterConsumptionPerUnit
- HazardousWastePerUnit
- NonHazardousWastePerUnit
- ClimateChangePerUnit
- AtmosphericAcidificationPerUnit
- RenewableEnergyConsumptionPerUnit
- NonRenewableEnergyConsumptionPerUnit
- ResourceDepletionPerUnit
- InertWastePerUnit
- RadioactiveWastePerUnit
- StratosphericOzoneLayerDestructionPerUnit
- PhotochemicalOzoneFormationPerUnit
- EutrophicationPerUnit
Pset_EnvironmentalImpactValues
- TotalPrimaryEnergyConsumption
- WaterConsumption
- HazardousWaste
- NonHazardousWaste
- ClimateChange
- AtmosphericAcidification
- RenewableEnergyConsumption
- NonRenewableEnergyConsumption
- ResourceDepletion
- InertWaste
- RadioactiveWaste
- StratosphericOzoneLayerDestruction
- PhotochemicalOzoneFormation
- Eutrophication
- LeadInTime
- Duration
- LeadOutTime
Pset_InstallationOccurrence
- InstallationDate
- AcceptanceDate
- PutIntoOperationDate
Pset_MaintenanceStrategy
- AssetCriticality
- AssetFrailty
- AssetPriority
- MonitoringType
- AccidentResponse
Pset_MaintenanceTriggerCondition
- ConditionTargetPerformance
- ConditionMaintenanceLevel
- ConditionReplacementLevel
- ConditionDisposalLevel
Pset_MaintenanceTriggerDuration
- DurationTargetPerformance
- DurationMaintenanceLevel
- DurationReplacementLevel
- DurationDisposalLevel
Pset_MaintenanceTriggerPerformance
- TargetPerformance
- PerformanceMaintenanceLevel
- ReplacementLevel
- DisposalLevel
Pset_ManufacturerOccurrence
- AcquisitionDate
- BarCode
- SerialNumber
- BatchReference
- AssemblyPlace
- ManufacturingDate
Pset_ManufacturerTypeInformation
- GlobalTradeItemNumber
- ArticleNumber
- ModelReference
- ModelLabel
- Manufacturer
- ProductionYear
- AssemblyPlace
- OperationalDocument
- SafetyDocument
- PerformanceCertificate
Pset_PrecastConcreteElementFabrication
- TypeDesignation
- ProductionLotId
- SerialNumber
- PieceMark
- AsBuiltLocationNumber
- ActualProductionDate
- ActualErectionDate
Pset_PrecastConcreteElementGeneral
- TypeDesignation
- CornerChamfer
- ManufacturingToleranceClass
- FormStrippingStrength
- LiftingStrength
- ReleaseStrength
- MinimumAllowableSupportLength
- InitialTension
- TendonRelaxation
- TransportationStrength
- SupportDuringTransportDescription
- SupportDuringTransportDocReference
- HollowCorePlugging
- CamberAtMidspan
- BatterAtStart
- BatterAtEnd
- Twisting
- Shortening
- PieceMark
- DesignLocationNumber
Pset_PrecastSlab
- TypeDesignation
- ToppingType
- EdgeDistanceToFirstAxis
- DistanceBetweenComponentAxes
- AngleToFirstAxis
- AngleBetweenComponentAxes
- NominalThickness
- NominalToppingThickness
Pset_ReinforcementBarPitchOfSlab
- Description
- Reference
- LongOutsideTopBarPitch
- LongInsideCenterTopBarPitch
- LongInsideEndTopBarPitch
- ShortOutsideTopBarPitch
- ShortInsideCenterTopBarPitch
- ShortInsideEndTopBarPitch
- LongOutsideLowerBarPitch
- LongInsideCenterLowerBarPitch
- LongInsideEndLowerBarPitch
- ShortOutsideLowerBarPitch
- ShortInsideCenterLowerBarPitch
- ShortInsideEndLowerBarPitch
Pset_RepairOccurrence
- RepairContent
- RepairDate
- MeanTimeToRepair
Pset_Risk
- RiskName
- RiskType
- NatureOfRisk
- RiskAssessmentMethodology
- UnmitigatedRiskLikelihood
- UnmitigatedRiskConsequence
- UnmitigatedRiskSignificance
- MitigationPlanned
- MitigatedRiskLikelihood
- MitigatedRiskConsequence
- MitigatedRiskSignificance
- MitigationProposed
- AssociatedProduct
- AssociatedActivity
- AssociatedLocation
Pset_ServiceLife
- ServiceLifeDuration
- MeanTimeBetweenFailure
Pset_SlabCommon
- Reference
- Status
- AcousticRating
- FireRating
- PitchAngle
- Combustible
- SurfaceSpreadOfFlame
- Compartmentation
- IsExternal
- ThermalTransmittance
- LoadBearing
Pset_SlabTypeTrackSlab TRACKSLAB
- TechnicalStandard
Pset_Tolerance
- ToleranceDescription
- ToleranceBasis
- OverallTolerance
- HorizontalTolerance
- OrthogonalTolerance
- VerticalTolerance
- PlanarFlatness
- HorizontalFlatness
- ElevationalFlatness
- SideFlatness
- OverallOrthogonality
- HorizontalOrthogonality
- OrthogonalOrthogonality
- VerticalOrthogonality
- OverallStraightness
- HorizontalStraightness
- OrthogonalStraightness
- VerticalStraightness
Pset_TrackBase BASESLAB
- IsSurfaceGalling
- SurfaceGallingArea
Pset_Uncertainty
- UncertaintyBasis
- UncertaintyDescription
- HorizontalUncertainty
- LinearUncertainty
- OrthogonalUncertainty
- VerticalUncertainty
Pset_Warranty
- WarrantyIdentifier
- WarrantyStartDate
- IsExtendedWarranty
- WarrantyPeriod
- WarrantyContent
- PointOfContact
- Exclusions
Qto_BodyGeometryValidation
- GrossSurfaceArea
- NetSurfaceArea
- GrossVolume
- NetVolume
- SurfaceGenusBeforeFeatures
- SurfaceGenusAfterFeatures
Qto_SlabBaseQuantities
- Width
- Length
- Depth
- Perimeter
- GrossArea
- NetArea
- GrossVolume
- NetVolume
- GrossWeight
- NetWeight

6.1.3.35.6 Concept usage

Brep representation — Figure 6.1.3.35.A — Building element body boundary representation

surface model — Figure 6.1.3.35.A — Building element body boundary representation

Concept	Usage	Description
IfcRoot (2)
Revision Control	General	Ownership, history, and merge state is captured using IfcOwnerHistory.
Software Identity	General	IfcRoot assigns the globally unique ID. In addition it may provide for a name and a description about the concept.
IfcObjectDefinition (9)
Classification Association	General	Any object occurrence or object type can have a reference to a specific classification reference, i.e. to a particular facet within a classification system.
Aggregation	General	No description available.
Approval Association	General	No description available.
Constraint Association	General	No description available.
Document Association	General	No description available.
Library Association	General	No description available.
Material Association	General	No description available.
Material Single	General	No description available.
Nesting	General	No description available.
IfcObject (5)
Object Predefined Type	General	No description available.
Object Typing	General	Any object occurrence can be typed by being assigned to a common object type utilizing this concept. A particular rule, restricting the applicable subtypes of IfcTypeObject that can be assigned, is introduced by overriding this concept at the level of subtypes of IfcObject. This concept can be applied to the following resources: IfcTypeObject
Object User Identity	General	An attribute Name and optionally Description can be used for all subypes of IfcObject. For those subtypes, that have an object type definition, such as IfcBeam - IfcBeamType, the common Name and optionally Description is associated with the object type.
Property Sets with Override	General	Any object occurrence can hold property sets, either directly at the object occurrence as element specific property sets, or at the object type, as type property sets. In this case, the properties that are provided to the object occurrence are the combinations of element specific and type properties. In case that the same property (within the same property set) is defined both in occurrence and type properties, the property value of the occurrence property overrides the property value of the type property.
Assignment to Group	General	No description available.
IfcProduct (18)
Body Geometry	General	The body or solid model geometric representation of an IfcProduct is typically defined using a Tessellation or Brep. Subtypes may provide recommendations on other representation types that may be used. The following attribute values for the IfcShapeRepresentation holding this geometric representation shall be used: IfcShapeRepresentation.RepresentationIdentifier = 'Body' IfcShapeRepresentation.RepresentationType = Typically 'Tessellation' or 'Brep'
Product Geometric Representation	General	The geometric representation of any IfcProduct is provided by the IfcProductDefinitionShape allowing multiple geometric representations. It uses the Product Placement concept utilizing IfcLocalPlacement to establish an object coordinate system, in which all geometric representations are founded. NOTE A detailed specification of how to apply the local placement and which shape representations are applicable is provided at the level of subtypes of IfcProduct and is further determined by the model view definition and implementer agreements.
Product Geometry Colour	General	No description available.
Product Geometry Layer	General	No description available.
Product Relative Positioning	General	If the IfcProduct Product Placement is placed relative to an IfcPositioningElement this relationship covers the information on which IfcPositioningElement positions the IfcProduct.
Product Span Positioning	General	No description available.
Box Geometry	General	No description available.
CoG Geometry	General	No description available.
Mapped Geometry	General	No description available.
Object Typing	General	This is a further elaboration on an inherited concept. This concept can be applied to the following resources: IfcTypeProduct
Product Local Placement	General	No description available.
Product Topology Representation	General	No description available.
Property Sets for Objects	General	This concept can be applied to the following resources: Pset_Risk Pset_Tolerance Pset_Uncertainty
Quantity Sets	General	This concept can be applied to the following resources: Qto_BodyGeometryValidation
Reference Geometry	General	No description available.
Reference SweptSolid Geometry	General	No description available.
Reference SweptSolid PolyCurve Geometry	General	No description available.
Reference Tessellation Geometry	General	No description available.
IfcElement (44)
Body AdvancedBrep Geometry	General	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 referred 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.
Body AdvancedSwept Directrix Geometry	General	No description available.
Body AdvancedSwept DiskSolid PolyCurve Geometry	General	No description available.
Body AdvancedSwept Tapered Geometry	General	No description available.
Body Brep Geometry	General	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. Figure 6.1.3.35.A — Building element body boundary representation EXAMPLE As shown in Figure 6.1.3.35.A, 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.
Body CSG Geometry	General	Any IfcElement (so far no further constraints are defined at the level of its subtypes) may be represented as 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.
Body SectionedSolidHorizontal	General	No description available.
Body SurfaceModel Geometry	General	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. Figure 6.1.3.35.B — Element surface model representation EXAMPLE As shown in Figure 6.1.3.35.B, 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.
Body SurfaceOrSolidModel Geometry	General	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.
Body SweptSolid Composite Geometry	General	No description available.
Body SweptSolid CompositeCurve Geometry	General	No description available.
Body SweptSolid ParameterizedProfile Geometry	General	No description available.
Body SweptSolid PolyCurve Geometry	General	No description available.
Body Tessellation Geometry	Reference View	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.
Box Geometry	General	This is a further elaboration on an inherited concept. Figure 6.1.3.35.C — Building element box representation EXAMPLE Any IfcElement may be represented by a bounding box, which shows the maximum extent of the body within the object coordinate system established by the IfcObjectPlacement. As shown in Figure 6.1.3.35.C, the bounding box representation is given by an IfcShapeRepresentation that includes a single item: an IfcBoundingBox.
CoG Geometry	General	This is a further elaboration on an inherited concept. 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 explicitly provided CoG created during export.
Element Interference	General	No description available.
Element Nesting	General	A host element can nest connected components. This should be used when there is a specific position or form factor to attach specific elements. EXAMPLE A sink has a pre-drilled hole to attach a faucet.
Element Projecting	General	No description available.
Element Voiding Features	General	No description available.
FootPrint Annotation Geometry	General	No description available.
FootPrint GeomSet PolyCurve Geometry	General	No description available.
FootPrint Geometry	General	No description available.
Mapped Geometry	General	This is a further elaboration on an inherited concept. 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.
Product Grid Placement	General	No description available.
Product Linear Placement	General	Product placement with a Product Linear Placement template. It defines the local coordinate system based on the curve which is referenced by IfcLinearPlacement.RelativePlacement which is an IfcAxis2PlacementLinear.Location using an IfcPointByDistanceExpression.BasisCurve. The local coordinate system is based on the tangent of the curve at Location, its normal in the global Z plane and the cross product of the aforementioned vectors.
Product Local Placement	General	This is a further elaboration on an inherited concept. 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.
Property Sets for Objects	General	This concept can be applied to the following resources: Pset_Condition Pset_InstallationOccurrence Pset_MaintenanceStrategy Pset_MaintenanceTriggerCondition Pset_MaintenanceTriggerDuration Pset_MaintenanceTriggerPerformance Pset_RepairOccurrence Pset_ConstructionAdministration Pset_ConstructionOccurence Pset_ElementKinematics Pset_EnvironmentalCondition Pset_EnvironmentalImpactIndicators Pset_EnvironmentalImpactValues Pset_ManufacturerOccurrence Pset_ManufacturerTypeInformation Pset_ServiceLife Pset_Warranty
Surface Feature Adherence	General	No description available.
Surface Sectioned Geometry	General	No description available.
Surface Tessellation Geometry	General	No description available.
Body AdvancedSweptSolid Geometry	General	No description available.
Body Clipping Geometry	General	No description available.
Body SweptSolid Geometry	General	No description available.
Element Covering	General	No description available.
Element Occurrence Attributes	General	No description available.
Element Voiding	General	No description available.
Lighting Geometry	General	No description available.
Object Typing	General	This concept can be applied to the following resources: IfcElementType
Profile 3D Geometry	General	No description available.
Profile Geometry	General	No description available.
Spatial Containment	General	This concept can be applied to the following resources: IfcSpatialElement
Surface 3D Geometry	General	No description available.
Surface Geometry	General	No description available.
IfcBuiltElement (3)
Product Assignment	General	This concept can be applied to the following resources: IfcTask - A task for operating on the slab.
Surface 3D Geometry	General	This is a further elaboration on an inherited concept. Some IfcBuiltElement may be represented by a surface as an abstract geometric representation. See each subtype for specific guidance.
Object Typing	General	This concept can be applied to the following resources: IfcBuiltElementType
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IfcSlab (12)
Body Clipping Geometry	General	This is a further elaboration on an inherited concept. The following constraints apply to the 'Clipping' representation: Solid: IfcExtrudedAreaSolid is required, Profile: IfcArbitraryClosedProfileDef, IfcRectangleProfileDef, IfcCircleProfileDef, IfcEllipseProfileDef shall be supported. Extrusion: The profile can be extruded perpendicularly or non-perpendicularly to the plane of the swept profile. Boolean result: The IfcBooleanClippingResult shall be supported, allowing for Boolean differences between the swept solid (here IfcExtrudedAreaSolid) and one or several IfcHalfSpaceSolid. Additional constraints apply when an IfcMaterialLayerSetUsage is used: Material: The definition of the IfcMaterialLayerSetUsage, particularly of the OffsetFromReferenceLine and the ForLayerSet.TotalThickness, has to be consistent to the 'SweptSolid' representation. Figure 6.1.3.35.D illustrates a 'Clipping' geometric representation with definition of a roof slab using advanced geometric representation. The profile is extruded non-perpendicular and the slab body is clipped at the eave. Figure 6.1.3.35.D — Slab body clipping
Body SweptSolid Geometry	General	This is a further elaboration on an inherited concept. The following constraints apply to the 'SweptSolid' representation: Solid: IfcExtrudedAreaSolid is required, Profile: IfcArbitraryClosedProfileDef, IfcRectangleProfileDef, IfcCircleProfileDef, IfcEllipseProfileDef shall be supported. Extrusion: The profile can be extruded perpendicularly or non-perpendicularly to the plane of the swept profile. For polygonal slabs, the following interpretation of dimension parameter applies: IfcArbitraryClosedProfileDef.OuterCurve: closed bounded curve interpreted as area (or foot print) of the slab. Additional constraints apply when an IfcMaterialLayerSetUsage is used: Material: The definition of the IfcMaterialLayerSetUsage, particularly of the OffsetFromReferenceLine and the ForLayerSet.TotalThickness, has to be consistent to the 'SweptSolid' representation. Figure 6.1.3.35.E — Slab body extrusion
Element Decomposition	General	A slab may be decomposed into parts such as for structural framing and covering panels or topping. For efficiency, each part may reuse geometry using the mapped geometry concept. Figure 6.1.3.35.F — A timber construction slab decomposed into parts. Figure 6.1.3.35.G — A section showing a slab made from precast hollow core panels This concept can be applied to the following resources: IfcBuildingElementPart - Parts for other elements IfcBeam - Precast hollow core planks or double tee beams in concrete construction, or joists and bearers in timber construction IfcCovering - Concrete or topping screeds IfcPlate - Used for metal decks at the base of slabs or sheathing
Element Voiding	General	This is a further elaboration on an inherited concept. As shown in Figure 6.1.3.35.H, openings within an aggregated slab are directly assigned to IfcSlab using IfcRelVoidsElement pointing to IfcOpeningElement and apply to all aggregated parts. If individual parts have cutting and other voiding features, then the decomposed parts have a separate voiding relationship IfcRelVoidsElement pointing to IfcVoidingFeature. Figure 6.1.3.35.H — How individual parts being cut may be expressed.
Material Layer Set Usage	General	Figure 6.1.3.35.I illustrates assignment of IfcMaterialLayerSetUsage and IfcMaterialLayerSet to the IfcSlabType and the IfcSlab occurrence. Figure 6.1.3.35.I — Slab type definition Figure 6.1.3.35.K and Figure 6.1.3.35.J illustrates material layer usage, where: The reference coordinate system is the coordinate system established by the IfcExtrudedAreaSolid.Position. The reference plane is the plane defined by the extruded profile of IfcExtrudedAreaSolid.SweptSolid. The IfcMaterialLayerSetUsage.OffsetFromReferenceLine is given as a distance from this plane. The IfcMaterialLayerSetUsage.DirectionSense defines how the IfcMaterialLayer's are assigned to the reference plane. POSITIVE means in direction to the positive z-axis of the reference coordinate system. The IfcMaterialLayerSetUsage.OffsetFromReferenceLine is the distance parallel to the reference plane and always perpendicular to the base (XY) plane of the reference coordinate system. This is independent of a potential non-perpendicular extrusion given by IfcExtrudedAreaSolid.ExtrudedDirection <> 0.,0.,1. A positive value of IfcMaterialLayerSetUsage.OffsetFromReferenceLine would then point into the positive z-axis of the reference coordinate system. The Thickness of each IfcMaterialLayer shall be the parallel distance (measured perpendicular to the base plane). The TotalThickness of the IfcMaterialLayerSet is the sum of all layer thicknesses and in case of a perpendicular extrusion identical with IfcExtrudedAreaSolid.Depth The IfcMaterialLayerSetUsage.LayerSetDirection is always AXIS3. The local placement of the slab uses the the x/y plane for the profile, and the z-axis as the extrusion direction for the slab body. Figure 6.1.3.35.J — Standard usage of a material layer set Figure 6.1.3.35.K — Material layers used in a sloping roof slab
Object Typing	General	This is a further elaboration on an inherited concept. This concept can be applied to the following resources: IfcSlabType
Product Assignment	General	This is a further elaboration on an inherited concept. This concept can be applied to the following resources: IfcStructuralSurfaceMember - An idealized structural member corresponding to the slab. IfcTask - A task for operating on the slab.
Property Sets for Objects	General	This is a further elaboration on an inherited concept. This concept can be applied to the following resources: Pset_ConcreteElementGeneral Pset_PrecastConcreteElementFabrication Pset_PrecastConcreteElementGeneral Pset_PrecastSlab Pset_ReinforcementBarPitchOfSlab Pset_SlabCommon Pset_TrackBase (only applies to `BASESLAB)` Pset_CessBetweenRails (only applies to `TRACKSLAB)` Pset_EmbeddedTrack (only applies to `TRACKSLAB)` Pset_SlabTypeTrackSlab (only applies to `TRACKSLAB)`
Quantity Sets	General	This is a further elaboration on an inherited concept. This concept can be applied to the following resources: Qto_SlabBaseQuantities
Spatial Containment	General	This is a further elaboration on an inherited concept. The IfcSlab, as any subtype of IfcBuiltElement, may participate alternatively in one of the two different containment relationships: the Spatial Containment (defined here), or the Element Composition.
Surface Geometry	General	This is a further elaboration on an inherited concept. The 'Surface' can be used to define a surfacic model of the building (e.g. for analytical purposes, or for reduced Level of Detail representation).
Material Set	General	This concept can be applied to the following resources: LoadBearing Insulation

6.1.3.35.7 Examples

Figure 6.1.3.35.L

Slab Openings
Figure 6.1.3.35.M

Slab Extrusion
Figure 6.1.3.35.N

Slab Tessellated Unique Vertices
Figure 6.1.3.35.O

Construction Scheduling Task

6.1.3.35.8 Formal representation

 ENTITY IfcSlab
 SUBTYPE OF (IfcBuiltElement);
	PredefinedType : OPTIONAL IfcSlabTypeEnum;
 WHERE
	CorrectPredefinedType : NOT(EXISTS(PredefinedType)) OR
 (PredefinedType <> IfcSlabTypeEnum.USERDEFINED) OR
 ((PredefinedType = IfcSlabTypeEnum.USERDEFINED) AND EXISTS (SELF\IfcObject.ObjectType));
	CorrectTypeAssigned : (SIZEOF(IsTypedBy) = 0) OR
  ('IFC4X3_DEV_738df036.IFCSLABTYPE' IN TYPEOF(SELF\IfcObject.IsTypedBy[1].RelatingType));
END_ENTITY;

6.1.3.35.9 References

IfcBuiltElement