IFC 4.3.x development

6.1.3.45 IfcSlabElementedCase

Change log

IFC4

added

6.1.3.45.1 Semantic definitions at the entity

The IfcSlabElementedCase defines a slab with certain constraints for the provision of its components. The IfcSlabElementedCase handles all cases of slabs, that are decomposed into parts:

HISTORY  New entity in IFC4.

Voiding Use Definition:

As shown in Figure 1, openings within the composite slab are directly assigned to IfcSlabElementedCase 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.

"voiding"

Formal Propositions

HasDecomposition

A valid instance of IfcSlabElementedCase has to have parts in a decomposition hierarchy.

# Attribute Type Description
IfcRoot
1 GlobalId IfcGloballyUniqueId Assignment of a globally unique identifier within the entire software world.
2 OwnerHistory OPTIONAL IfcOwnerHistory Assignment of the information about the current ownership of that object, including owning actor, application, local identification and information captured about the recent changes of the object,

> NOTE  only the last modification in stored - either as addition, deletion or modification.

> IFC4 CHANGE  The attribute has been changed to be OPTIONAL.
3 Name OPTIONAL IfcLabel Optional name for use by the participating software systems or users. For some subtypes of IfcRoot the insertion of the Name attribute may be required. This would be enforced by a where rule.
4 Description OPTIONAL IfcText Optional description, provided for exchanging informative comments.
IfcObjectDefinition
HasAssignments SET [0:?] OF IfcRelAssigns FOR RelatedObjects Reference to the relationship objects, that assign (by an association relationship) other subtypes of IfcObject to this object instance. Examples are the association to products, processes, controls, resources or groups.
Nests SET [0:1] OF IfcRelNests FOR RelatedObjects References to the decomposition relationship being a nesting. It determines that this object definition is a part within an ordered whole/part decomposition relationship. An object occurrence or type can only be part of a single decomposition (to allow hierarchical strutures only).

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

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

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

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

> IFC4 CHANGE  The inverse attribute datatype has been changed from the supertype IfcRelDecomposes to subtype IfcRelAggregates.
HasAssociations SET [0:?] OF IfcRelAssociates FOR RelatedObjects Reference to the relationship objects, that associates external references or other resource definitions to the object.. Examples are the association to library, documentation or classification.
IfcObject
5 ObjectType OPTIONAL IfcLabel The type denotes a particular type that indicates the object further. The use has to be established at the level of instantiable subtypes. In particular it holds the user defined type, if the enumeration of the attribute PredefinedType is set to USERDEFINED.
IsDeclaredBy SET [0:1] OF IfcRelDefinesByObject FOR RelatedObjects Link to the relationship object pointing to the declaring object that provides the object definitions for this object occurrence. The declaring object has to be part of an object type decomposition. The associated IfcObject, or its subtypes, contains the specific information (as part of a type, or style, definition), that is common to all reflected instances of the declaring IfcObject, or its subtypes.

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

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

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

> IFC4 CHANGE  The data type has been changed from IfcRelDefines to IfcRelDefinesByProperties with upward compatibility for file based exchange.
IfcProduct
6 ObjectPlacement OPTIONAL IfcObjectPlacement Placement of the product in space, the placement can either be absolute (relative to the world coordinate system), relative (relative to the object placement of another product), or constraint (e.g. relative to grid axes). It is determined by the various subtypes of IfcObjectPlacement, which includes the axis placement information to determine the transformation for the object coordinate system.
7 Representation OPTIONAL IfcProductRepresentation Reference to the representations of the product, being either a representation (IfcProductRepresentation) or as a special case a shape representations (IfcProductDefinitionShape). The product definition shape provides for multiple geometric representations of the shape property of the object within the same object coordinate system, defined by the object placement.
ReferencedBy SET [0:?] OF IfcRelAssignsToProduct FOR RelatingProduct Reference to the IfcRelAssignsToProduct relationship, by which other products, processes, controls, resources or actors (as subtypes of IfcObjectDefinition) can be related to this product.
PositionedRelativeTo SET [0:?] OF IfcRelPositions FOR RelatedProducts
ReferencedInStructures SET [0:?] OF IfcRelReferencedInSpatialStructure FOR RelatedElements
IfcElement
8 Tag OPTIONAL IfcIdentifier The tag (or label) identifier at the particular instance of a product, e.g. the serial number, or the position number. It is the identifier at the occurrence level.
FillsVoids SET [0:1] OF IfcRelFillsElement FOR RelatedBuildingElement Reference to the IfcRelFillsElement Relationship that puts the element as a filling into the opening created within another element.
ConnectedTo SET [0:?] OF IfcRelConnectsElements FOR RelatingElement Reference to the element connection relationship. The relationship then refers to the other element to which this element is connected to.
IsInterferedByElements SET [0:?] OF IfcRelInterferesElements FOR RelatedElement Reference to the interference relationship to indicate the element that is interfered. The relationship, if provided, indicates that this element has an interference with one or many other elements.

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

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

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

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

6.1.3.45.1 Entity inheritance

dot_inheritance IfcSlabElementedCase IfcSlabElementedCase IfcSlab IfcSlab IfcSlabElementedCase->IfcSlab IfcSlabStandardCase IfcSlabStandardCase IfcSlabStandardCase->IfcSlab IfcBuiltElement IfcBuiltElement IfcSlab->IfcBuiltElement IfcBuiltElement_children 24 more... IfcBuiltElement_children->IfcBuiltElement IfcElement IfcElement IfcBuiltElement->IfcElement IfcElement_children 10 more... IfcElement_children->IfcElement IfcProduct IfcProduct IfcElement->IfcProduct IfcProduct_children 8 more... IfcProduct_children->IfcProduct IfcObject IfcObject IfcProduct->IfcObject IfcObject_children 5 more... IfcObject_children->IfcObject IfcObjectDefinition IfcObjectDefinition IfcObject->IfcObjectDefinition IfcContext IfcContext IfcContext->IfcObjectDefinition IfcRoot IfcRoot IfcObjectDefinition->IfcRoot IfcTypeObject IfcTypeObject IfcTypeObject->IfcObjectDefinition IfcPropertyDefinition IfcPropertyDefinition IfcPropertyDefinition->IfcRoot IfcRelationship IfcRelationship IfcRelationship->IfcRoot

6.1.3.45.2 Definitions applying to General Usage

6.1.3.45.2.1 Aggregation

The following guidance is provided for the components of the IfcSlabElementedCase. The following component entity types should be used:

6.1.3.45.2.2 Body AdvancedBrep Geometry

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

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

6.1.3.45.2.3 Body Brep Geometry

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

 

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

Figure 150 — Building element body boundary representation

 

6.1.3.45.2.4 Body CSG Geometry

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

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

6.1.3.45.2.5 Body Clipping Geometry

The following constraints apply to the 'Clipping' representation:

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

Figure 266 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.

advanced slab

Figure 266 — Slab body clipping

The following constraints apply to the 'Clipping' representation, when an IfcMaterialLayerSetUsage is assigned to the IfcSlab:

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

 

advanced slab
EXAMPLE  Figure 267 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 267 — Slab body clipping

 

6.1.3.45.2.6 Body SurfaceModel Geometry

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

 

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

Figure 149 — Element surface model representation

 

6.1.3.45.2.7 Body SurfaceOrSolidModel Geometry

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

6.1.3.45.2.8 Body SweptSolid Geometry

The following constraints apply to the 'SweptSolid' representation:

Figure 264 illustrates a 'SweptSolid' geometric representation.

NOTE  The following interpretation of dimension parameter applies for polygonal slabs (in ground floor view):
standard slab

Figure 264 — Slab body extrusion

The following additional constraints apply to the 'SweptSolid' representation, when an IfcMaterialLayerSetUsage is assigned to the IfcSlab:

 

standard slab
EXAMPLE  Figure 265 illustrates a 'SweptSolid' geometric representation. The following interpretation of dimension parameter applies for polygonal slabs (in ground floor view): IfcArbitraryClosedProfileDef.OuterCurve: closed bounded curve interpreted as area (or foot print) of the slab.

Figure 265 — Slab body extrusion

 

6.1.3.45.2.9 Body Tessellation Geometry

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

6.1.3.45.2.10 Box Geometry

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

Figure 148 — Building element box representation

 

6.1.3.45.2.11 Classification Association

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

6.1.3.45.2.12 CoG Geometry

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

6.1.3.45.2.13 Element Projecting

6.1.3.45.2.14 Element Voiding

6.1.3.45.2.15 FootPrint Geometry

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

6.1.3.45.2.16 Identity

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

6.1.3.45.2.17 Mapped Geometry

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

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

6.1.3.45.2.18 Material Layer Set

The material information of the IfcSlab is defined by IfcMaterialLayerSet, or as fallback by IfcMaterial, and it is attached either directly or at the IfcSlabType. In this case, the material information does not allow to construct a shape by applying the layer definition to the plane of the shape representation, to enable this parametric definition, the IfcMaterialLayerSetUsage has to be used instead.

6.1.3.45.2.19 Material Layer Set Usage

The material of IfcSlab can be defined by IfcMaterialLayerSetUsage and attached by IfcRelAssociatesMaterial.RelatingMaterial. It is accessible by the inverse HasAssociations relationship. Multi-layer slabs can be represented by refering to several IfcMaterialLayer's within the IfcMaterialLayerSet that is referenced from th e IfcMaterialLayerSetUsage.

When assigning an IfcMaterialLayerSetUsage to IfcSlab it shall imply that the IfcSlabType should have a unique IfcMaterialLayerSet, that is referenced by IfcMaterialLayerSetUsage assigned to all occurrences of this IfcSlabType.

Material layer set and usage
EXAMPLE  Figure 262 illustrates assignment of IfcMaterialLayerSetUsage and IfcMaterialLayerSet to the IfcSlab as the slab occurrence and to the IfcSlabType. The same IfcMaterialLayerSet shall be shared by many occurrences of IfcMaterialLayerSetUsage. This relationship shall be consistent to the relationship between the IfcSlabType and the IfcSlabStandardCase.

Figure 262 — Slab type definition

 

Figure 263 illustrates slab material usage, where the following conventions shall be met:

  • 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.
slab material layer set
roof slab material layer set

Figure 263 — Slab material layers

6.1.3.45.2.20 Object Predefined Type

6.1.3.45.2.21 Object Typing

RelatingType
'IfcSlabType'

6.1.3.45.2.22 Object User Identity

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

6.1.3.45.2.23 Placement

The use of local placement is defined at the supertype IfcSlab. The local placement of the IfcSlabElementedCase defines the parent coordinate systems for the parts within the decomposition. All parts shall be positioned relative to the IfcSlabElementedCase.

6.1.3.45.2.24 Product Geometric Representation

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

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

6.1.3.45.2.25 Product Local Placement

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.

HasPlacement
'IfcLocalPlacement'
'IfcLocalPlacement'

6.1.3.45.2.26 Product Placement

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

6.1.3.45.2.27 Property Sets for Objects

PsetName
'Pset_SlabCommon'
'Pset_ConcreteElementGeneral'
'Pset_PrecastConcreteElementFabrication'
'Pset_PrecastConcreteElementGeneral'
'Pset_PrecastSlab'
'Pset_ReinforcementBarPitchOfSlab'
'Pset_EnvironmentalImpactIndicators'
'Pset_EnvironmentalImpactValues'
'Pset_Condition'
'Pset_ManufacturerOccurrence'
'Pset_ManufacturerTypeInformation'
'Pset_ServiceLife'
'Pset_Warranty'

6.1.3.45.2.28 Property Sets with Override

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

6.1.3.45.2.29 Quantity Sets

QsetName
'Qto_SlabBaseQuantities'

6.1.3.45.2.30 Revision Control

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

6.1.3.45.2.31 Spatial Containment

The IfcSlab, 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.
RelatingStructure
'IfcBuildingStorey'
'IfcBuilding'
'IfcSite'

6.1.3.45.2.32 Surface Geometry

A three-dimensional surface being a subtype of IfcBoundedSurface defining the reference surface for the elemented slab. It maybe used as a simplified representation directly at the elemented slab.

NOTE  It is invalid to exhange a 'Body' shape representation of an IfcSlabElementedCase. The body geometry is defined by the parts within the decomposition.
NOTE  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). It should suppress the geometric details of the parts in the decomposition.

6.1.3.45.3 Formal representations

ENTITY IfcSlabElementedCase
 SUBTYPE OF (IfcSlab);
 WHERE
	HasDecomposition : HIINDEX(SELF\IfcObjectDefinition.IsDecomposedBy) > 0;
END_ENTITY;