#### IfcBuildingElement

Natural language names

##### Semantic definitions at the entity

Entity definition

Definition from ISO 6707-1:1989: Major functional part of a building, examples are foundation, floor, roof, wall.

The building element comprises all elements that are primarily part of the construction of a building, i.e., its structural and space separating system.

> EXAMPLEs of building elements are walls, beams, or doors, they are all physically existent and tangible things.

The IfcBuildingElement utilizes the following capabilities mainly through inverse attributes referencing objectified relationships:

1. Grouping - being part of a logical group of objects
   - objectified relationship: IfcRelAssignsToGroup
   - inverse attribute: HasAssignment
2. Work processes - reference to work tasks, in which this building element is used
   - objectified relationship: IfcRelAssignsToProcess
   - inverse attribute: HasAssignments
3. Aggregation - aggregated together with other elements to form an aggregate
   - objectified relationship: IfcRelAggregates
   - inverse attribute (for container): IsDecomposedBy
   - inverse attribute (for contained parts): Decomposes
4. Material - assignment of material used by this building element
   - objectified relationship: IfcRelAssociatesMaterial
   - inverse attribute: HasAssociations
5. Classification - assigned reference to an external classification
   - objectified relationship: IfcRelAssociatesClassification
   - inverse attribute: HasAssociations
6. Documentation - assigned reference to an external documentation
   - objectified relationship: IfcRelAssociatesDocumentation
   - inverse attribute: HasAssociations
7. Type - reference to the common product type information for the element occurrence
   - objectified relationship: IfcRelDefinesByType
   - inverse attribute: IsDefinedBy
8. Properties - reference to all attached properties, including quantities
   - objectified relationship: IfcRelDefinesByProperties
   - inverse attribute: IsDefinedBy
9. Connection - connectivity to other elements, including the definition of the joint
   - objectified relationship: IfcRelConnectsElements
   - inverse attribute: ConnectedTo
   - inverse attribute: ConnectedFrom
10. Realization - information, whether the building element is used to realize a connection (e.g. as a weld in a connection between two members)
    - objectified relationship: IfcRelConnectsWithRealizingElements
    - inverse attribute: IsConnectionRealization
11. Ports - information, whether the building element has ports for system connections (note: normally not used, this relationship is inherited from IfcElement and mainly applicable to IfcDistributionElement's)
    - objectified relationship: IfcRelConnectsPortToElement
    - inverse attribute: HasPorts
12. Assignment to spatial structure - hierarchical assignment to the right level within the spatial structure
    - objectified relationship: IfcRelContainedInSpatialStructure
    - inverse attribute: ContainedInStructure
13. Reference to spatial structure(s) - non hierarchical reference to one or more elements within the spatial structure (e.g. a curtain wall, being contained in the building, references several stories)
    - objectified relationship: IfcRelContainedInSpatialStructure
    - inverse attribute: ContainedInStructure
14. Boundary - provision of space boundaries by this building element
    - objectified relationship: IfcRelSpaceBoundary
    - inverse attribute: ProvidesBoundaries
15. Coverings - assignment of covering elements to this building element (note: normally covering elements are assigned to the space, only used for special cases)
    - objectified relationship: IfcRelCoversBldgElements
    - inverse attribute: HasCoverings
16. Voids - information, whether the building element includes openings, recesses or other voids
    - objectified relationship: IfcRelVoidsElement
    - inverse attribute: HasOpenings
17. Projection - information, whether the building element has projections (such as a fascia)
    - objectified relationship: IfcRelProjectsElement
    - inverse attribute: HasProjections
18. Filling - information whether the building element is used to fill openings
    - objectified relationship: IfcRelFillsElement
    - inverse attribute: FillsVoids
19. Structural member reference - information whether the building element is represented in a structural analysis model by a structural member
    - objectified relationship: IfcRelConnectsStructuralElement
    - inverse attribute: HasStructuralMember

> HISTORY New entity in IFC Release 1.0

Quantity Use Definition:

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

Geometry Use Definitions

The geometric representation of any IfcBuildingElement is given by the IfcProductDefinitionShape and IfcLocalPlacement allowing multiple geometric representations.

Local Placement

The local placement for any IfcBuildingElement 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. Further constraints are defined at the level of its subtypes.

Geometric Representations

Any IfcBuildingElement can be represented by one or several geometric representations. A detailed specification is introduced at the level of subtypes. Only the general representation types 'BoundingBox', 'SurfaceModel', 'Brep', and 'MappedRepresentation' are defined here.

Bounding Box Representation

Any IfcBuildingElement may be represented as a bounding box, which shows the maximum extend of the body within the coordinated system established by the IfcLocalPlacement. The bounding box representation is the simplest geometric representation available. The following attribute values for the IfcShapeRepresentation holding this geometric representation shall be used:

- RepresentationIdentifier : 'Box' Body
- RepresentationType : 'BoundingBox'

| The bounding box representation is given by an IfcShapeRepresentation, which includes a single item, an IfcBoundingBox.

SurfaceModel Representation

Any IfcBuildingElement (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 models. The following attribute values for the IfcShapeRepresentation holding this geometric representation shall be used:

- RepresentationIdentifier : 'Body'
- RepresentationType : 'SurfaceModel'

In some cases it may be useful to also expose a simple representation as a bounding box representation of the same complex shape.

| The surface model representation is given by an IfcShapeRepresentation, which includes a single item, which is either: IfcShellBasedSurfaceModel, or IfcFaceBasedSurfaceModel.

Brep Representation

Any IfcBuildingElement (so far no further constraints are defined at the level of its subtypes) may be represented as a single or multiple Boundary Representation elements (which are restricted to faceted Brep with or without voids). The Brep representation allows for the representation of complex element shape. The following attribute values for the IfcShapeRepresentation holding this geometric representation shall be used:

- RepresentationIdentifier : 'Body'
- RepresentationType : 'Brep'

In some cases it may be useful to also expose a simple representation as a bounding box representation of the same complex shape.

| TheBrep representation is given by an IfcShapeRepresentation, which includes one or more items, all of type IfcManifoldSolidBrep.

MappedRepresentation

Any IfcBuildingElement (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 following attribute values for the IfcShapeRepresentation holding this geometric representation shall be used:

- RepresentationIdentifier : 'Body'
- RepresentationType : 'MappedRepresentation'

The same constraints, as given for the 'SurfaceModel' and the 'Brep' geometric representation, shall apply to the MappedRepresentation of the IfcRepresentationMap.

##### Inherited definitions from supertypes

Entity inheritance
Attribute inheritance

# | Attribute | Type | Cardinality | Description | A
--- | --- | --- | --- | --- | ---
IfcRoot
1 | GlobalId | IfcGloballyUniqueId | [1:1] | Assignment of a globally unique identifier within the entire software world. | X
2 | OwnerHistory | IfcOwnerHistory | [1:1] | Assignment of the information about the current ownership of that object, including owning actor, application, local identification and information captured about the recent changes of the object, NOTE: only the last modification in stored. | X
3 | Name | IfcLabel | [0:1] | Optional name for use by the participating software systems or users. For some subtypes of IfcRoot the insertion of the Name attribute may be required. This would be enforced by a where rule. | X
4 | Description | IfcText | [0:1] | Optional description, provided for exchanging informative comments. | X
IfcObjectDefinition
| IsDecomposedBy | IfcRelDecomposes @RelatingObject | S[0:?] | Reference to the decomposition relationship, that allows this object to be the composition of other objects. An object can be decomposed by several other objects. | X
| Decomposes | IfcRelDecomposes @RelatedObjects | S[0:1] | References to the decomposition relationship, that allows this object to be a part of the decomposition. An object can only be part of a single decomposition (to allow hierarchical strutures only). | X
| HasAssociations | IfcRelAssociates @RelatedObjects | S[0:?] | Reference to the relationship objects, that associates external references or other resource definitions to the object.. Examples are the association to library, documentation or classification. | X
IfcObject
5 | ObjectType | IfcLabel | [0:1] | The type denotes a particular type that indicates the object further. The use has to be established at the level of instantiable subtypes. In particular it holds the user defined type, if the enumeration of the attribute PredefinedType is set to USERDEFINED. | X
| IsDefinedBy | IfcRelDefines @RelatedObjects | S[0:?] | Set of relationships to type or property (statically or dynamically defined) information that further define the object. In case of type information, the associated IfcTypeObject contains the specific information (or type, or style), that is common to all instances of IfcObject referring to the same type. | X
IfcProduct
6 | ObjectPlacement | IfcObjectPlacement | [0:1] | Placement of the product in space, the placement can either be absolute (relative to the world coordinate system), relative (relative to the object placement of another product), or constraint (e.g. relative to grid axes). It is determined by the various subtypes of IfcObjectPlacement, which includes the axis placement information to determine the transformation for the object coordinate system. | X
7 | Representation | IfcProductRepresentation | [0:1] | Reference to the representations of the product, being either a representation (IfcProductRepresentation) or as a special case a shape representations (IfcProductDefinitionShape). The product definition shape provides for multiple geometric representations of the shape property of the object within the same object coordinate system, defined by the object placement. | X
IfcElement
8 | Tag | - |  | This attribute is out of scope for this model view definition and shall not be set. |
| ConnectedTo | IfcRelConnectsElements @RelatingElement | S[0:?] | Reference to the element connection relationship. The relationship then refers to the other element to which this element is connected to. |
| HasOpenings | IfcRelVoidsElement @RelatingBuildingElement | S[0:?] | Reference to the Voids Relationship that creates an opening in an element. An element can incorporate zero-to-many openings. | X
| IsConnectionRealization | IfcRelConnectsWithRealizingElements @RealizingElements | S[0:?] | Reference to the connection relationship with realizing element. The relationship then refers to the realizing element which provides the physical manifestation of the connection relationship. | X
| ConnectedFrom | IfcRelConnectsElements @RelatedElement | S[0:?] | Reference to the element connection relationship. The relationship then refers to the other element that is connected to this element. | X
| ContainedInStructure | IfcRelContainedInSpatialStructure @RelatedElements | S[0:1] | Containment relationship to the spatial structure element, to which the element is primarily associated. | X
IfcBuildingElement

##### Formal representations

XSD Specification
`<xs:element name="IfcBuildingElement" type="ifc:IfcBuildingElement" abstract="true" substitutionGroup="ifc:IfcElement" nillable="true"/>
<xs:complexType name="IfcBuildingElement" abstract="true">
<xs:complexContent>
<xs:extension base="ifc:IfcElement"/>
</xs:complexContent>
</xs:complexType>
`
EXPRESS Specification
`ENTITY IfcBuildingElement
ABSTRACT SUPERTYPE OF(ONEOF(IfcBeam, IfcColumn, IfcCovering, IfcMember, IfcPlate, IfcRailing, IfcStair, IfcStairFlight))
SUBTYPE OF (IfcElement);
END_ENTITY;

EXPRESS-G diagram

`

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