#### 6.1.3.6 IfcSlab

| Decke / Dachfläche / Bodenplatte
| Dalle

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

> NOTE Definition according to ISO 6707-1
> thick, flat or shaped component, usually larger than 300 mm square, used to form a covering or projecting from 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.

> NOTE There is a representation of slabs for structural analysis provided by a proper subtype of IfcStructuralMember being part of the IfcStructuralAnalysisModel.

> NOTE An arbitrary planar element to which this semantic information is not applicable or irrelevant shall be modeled as IfcPlate.

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.

There are three entities for slab occurrences:

- IfcSlabStandardCase 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. In addition they have to have a corresponding IfcMaterialLayerSetUsage assigned.
- IfcSlabElementedCase used for occurrences of slabs which are aggregated from subordinate elements, following specific decomposition rules expressed by the mandatory use of IfcRelAggregates relationship.
- IfcSlab 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.

> HISTORY New entity in IFC2.0; it is a merger of the two previous entities IfcFloor, IfcRoofSlab, introduced in IFC1.0

XSD Specification:

<xs:element name="IfcSlab" type="ifc:IfcSlab" substitutionGroup="ifc:IfcBuildingElement" nillable="true"/>
<xs:complexType name="IfcSlab">
<xs:complexContent>
<xs:extension base="ifc:IfcBuildingElement"/>
</xs:complexContent>
</xs:complexType>

EXPRESS Specification:

ENTITY IfcSlab

| SUPERTYPE OF(IfcSlabElementedCase)

| SUBTYPE OF (IfcBuildingElement);

PredefinedType | : | OPTIONAL IfcStrippedOptional;

| WHERE

CorrectPredefinedType | : | NOT(EXISTS(PredefinedType)) OR (PredefinedType <> IfcSlabTypeEnum.USERDEFINED) OR ((PredefinedType = IfcSlabTypeEnum.USERDEFINED) AND EXISTS (SELF\IfcObject.ObjectType));
CorrectTypeAssigned | : | (SIZEOF(IsTypedBy) = 0) OR ('IFCSHAREDBLDGELEMENTS.IFCSLABTYPE' IN TYPEOF(SELF\IfcObject.IsTypedBy[1].RelatingType));

END_ENTITY;

Attribute Definitions:

Formal Propositions:

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.
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.

Inheritance Graph:

ENTITY IfcSlab

| ENTITY IfcRoot

GlobalId | : | IfcGloballyUniqueId;
OwnerHistory | : | OPTIONAL IfcOwnerHistory;
Name | : | OPTIONAL IfcLabel;
Description | : | OPTIONAL IfcText;

| ENTITY IfcObjectDefinition

| INVERSE

HasAssignments | : | SET OF IfcRelAssigns FOR RelatedObjects;
Nests | : | SET [0:1] OF IfcRelNests FOR RelatedObjects;
IsNestedBy | : | SET OF IfcRelNests FOR RelatingObject;
HasContext | : | SET [0:1] OF IfcRelDeclares FOR RelatedDefinitions;
IsDecomposedBy | : | SET OF IfcRelAggregates FOR RelatingObject;
Decomposes | : | SET [0:1] OF IfcRelAggregates FOR RelatedObjects;
HasAssociations | : | SET OF IfcRelAssociates FOR RelatedObjects;

| ENTITY IfcObject

ObjectType | : | OPTIONAL IfcStrippedOptional;

| INVERSE

IsDeclaredBy | : | SET [0:1] OF IfcRelDefinesByObject FOR RelatedObjects;
Declares | : | SET OF IfcRelDefinesByObject FOR RelatingObject;
IsTypedBy | : | SET [0:1] OF IfcRelDefinesByType FOR RelatedObjects;
IsDefinedBy | : | SET OF IfcRelDefinesByProperties FOR RelatedObjects;

| ENTITY IfcProduct

ObjectPlacement | : | OPTIONAL IfcObjectPlacement;
Representation | : | OPTIONAL IfcProductRepresentation;

| INVERSE

ReferencedBy | : | SET OF IfcRelAssignsToProduct FOR RelatingProduct;

| ENTITY IfcElement

Tag | : | OPTIONAL IfcStrippedOptional;

| INVERSE

IsInterferedByElements | : | SET OF IfcRelInterferesElements FOR RelatedElement;
InterferesElements | : | SET OF IfcRelInterferesElements FOR RelatingElement;
ContainedInStructure | : | SET [0:1] OF IfcRelContainedInSpatialStructure FOR RelatedElements;

| ENTITY IfcBuildingElement

| INVERSE

| ENTITY IfcSlab

PredefinedType | : | OPTIONAL IfcStrippedOptional;

END_ENTITY;

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