#### IfcSpatialStructureElement

Natural language names

##### Semantic definitions at the entity

Entity definition

A spatial structure element (IfcSpatialStructureElement) is the generalization of all spatial elements that might be used to define a spatial structure. That spatial structure is often used to provide a project structure to organize a building project.

A spatial project structure might define as many levels of decomposition as necessary for the building project. Elements within the spatial project structure are:

- site as IfcSite
- building as IfcBuilding
- storey as IfcBuildingStorey
- space as IfcSpace

or aggregations or parts thereof. The composition type declares an element to be either an element itself, or an aggregation (complex) or a decomposition (part). The interpretation of these types is given at each subtype of IfcSpatialStructureElement.

The IfcRelAggregates is defined as an 1-to-many relationship and used to establish the relationship between exactly two levels within the spatial project structure. Finally the highest level of the spatial structure is assigned to IfcProject using the IfcRelAggregates.

Informal proposition:

1. The spatial project structure, established by the IfcRelAggregates, shall be acyclic.
2. A site should not be (directly or indirectly) associated to a building, storey or space.
3. A building should not be (directly or indirectly) associated to a storey or space.
4. A storey should not be (directly or indirectly) associated to a space.

> HISTORY New entity in IFC Release 2x.

Spatial Structure Use Definition

| The figure shows the use of IfcRelAggregates to establish a spatial structure including site, building, building section and storey. More information is provided at the level of the subtypes.

Attribute definitions

# | Attribute | Type | Cardinality | Description | A
--- | --- | --- | --- | --- | ---
8 | LongName | - |  | This attribute is out of scope for this model view definition and shall not be set. |
9 | CompositionType | IfcElementCompositionEnum | [1:1] | Denotes, whether the predefined spatial structure element represents itself, or an aggregate (complex) or a part (part). The interpretation is given separately for each subtype of spatial structure element. | X
| ContainsElements | IfcRelContainedInSpatialStructure @RelatingStructure | S[0:?] | Set of spatial containment relationships, that holds those elements, which are contained within this element of the project spatial structure. NOTE The spatial containment relationship, established by IfcRelContainedInSpatialStructure, is required to be an hierarchical relationship, i.e. each element can only be assigned to 0 or 1 spatial structure element. | X

Formal Propositions

Rule | Description
--- | ---
WR41 | All spatial structure elements shall be associated (using the IfcRelAggregates relationship) with another spatial structure element, or with IfcProject.

##### 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
IfcSpatialStructureElement
8 | LongName | - |  | This attribute is out of scope for this model view definition and shall not be set. |
9 | CompositionType | IfcElementCompositionEnum | [1:1] | Denotes, whether the predefined spatial structure element represents itself, or an aggregate (complex) or a part (part). The interpretation is given separately for each subtype of spatial structure element. | X
| ContainsElements | IfcRelContainedInSpatialStructure @RelatingStructure | S[0:?] | Set of spatial containment relationships, that holds those elements, which are contained within this element of the project spatial structure. NOTE The spatial containment relationship, established by IfcRelContainedInSpatialStructure, is required to be an hierarchical relationship, i.e. each element can only be assigned to 0 or 1 spatial structure element. | X

##### Formal representations

XSD Specification
`<xs:element name="IfcSpatialStructureElement" type="ifc:IfcSpatialStructureElement" abstract="true" substitutionGroup="ifc:IfcProduct" nillable="true"/>
<xs:complexType name="IfcSpatialStructureElement" abstract="true">
<xs:complexContent>
<xs:extension base="ifc:IfcProduct">
<xs:attribute name="CompositionType" type="ifc:IfcElementCompositionEnum" use="optional"/>
</xs:extension>
</xs:complexContent>
</xs:complexType>
`
EXPRESS Specification
`ENTITY IfcSpatialStructureElement
ABSTRACT SUPERTYPE OF(ONEOF(IfcBuilding, IfcBuildingStorey, IfcSite))
SUBTYPE OF (IfcProduct);
LongName : OPTIONAL IfcStrippedOptional;
CompositionType : IfcElementCompositionEnum;
INVERSE
ContainsElements : SET [0:?] OF IfcRelContainedInSpatialStructure FOR RelatingStructure;
WHERE
WR41 : (HIINDEX(SELF\IfcObjectDefinition.Decomposes) = 1) AND ('IFCKERNEL.IFCRELAGGREGATES' IN TYPEOF(SELF\IfcObjectDefinition.Decomposes[1])) AND (('IFCKERNEL.IFCPROJECT' IN TYPEOF (SELF\IfcObjectDefinition.Decomposes[1].RelatingObject)) OR ('IFCPRODUCTEXTENSION.IFCSPATIALSTRUCTUREELEMENT' IN TYPEOF (SELF\IfcObjectDefinition.Decomposes[1].RelatingObject)) );
END_ENTITY;

EXPRESS-G diagram

`

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