IfcElementAssembly

Natural language names
dezusammengesetztes Element
enElement Assembly
frAssemblage d'éléments
Change log
ItemSPFXMLChangeDescription
IFC2x3 to IFC4
    IfcElementAssembly
      OwnerHistoryMODIFIEDInstantiation changed to OPTIONAL.
      PredefinedTypeMODIFIEDInstantiation changed to OPTIONAL.
IFC4 Addendum 1
    IfcElementAssembly
      HasCoveringsADDED
Semantic definitions at the entity
Entity definition

The IfcElementAssembly represents complex element assemblies aggregated from several elements, such as discrete elements, building elements, or other elements.

EXAMPLE Steel construction assemblies, such as trusses and different kinds of frames, can be represented by the IfcElementAssembly entity. Other examples include slab fields aggregated from a number of precast concrete slabs or reinforcement units made from several reinforcement bars. Also bathroom units, staircase sections and other premanufactured or precast elements are examples of the general IfcElementAssembly entity
NOTE  The IfcElementAssembly is a general purpose entity that is required to be decomposed. Also other subtypes of IfcElement can be decomposed, with some dedicated entities such as IfcWallElementedCase and IfcSlabElementedCase.

The assembly structure can be nested, i.e. an IfcElementAssembly could be an aggregated part within another IfcElementAssembly.

NOTE  View definitions and/or implementer agreements may restrict the number of allowed levels of nesting.

The geometry of an IfcElementAssembly is generally formed from its components, in which case it does not need to have an explicit geometric representation. In some cases it may be useful to also expose an own explicit representation of the aggregate.

NOTE  View definitions or implementer agreements may further constrain the applicability of certain shape representations at the IfcElementAssembly in respect of the shape representations of its parts.
HISTORY  New entity in IFC2x2.

Informal Propositions:

  1. The IfcElementAssembly shall have an aggregation relationship to the contained parts, i.e. the (INV) IsDecomposedBy relationship shall be utilzed.
Attribute definitions
#AttributeTypeCardinalityDescription C
9AssemblyPlaceIfcAssemblyPlaceEnum[0:1] A designation of where the assembly is intended to take place defined by an Enum.X
10PredefinedTypeIfcElementAssemblyTypeEnum[0:1] Predefined generic types for a element assembly that are specified in an enumeration. There might be property sets defined specifically for each predefined type. X
Formal Propositions
RuleDescription
CorrectPredefinedTypeEither the PredefinedType attribute is unset (e.g. because an IfcElementAssemblyType is associated), or the inherited attribute ObjectType shall be provided, if the PredefinedType is set to USERDEFINED.
CorrectTypeAssignedEither there is no element assembly type object associated, i.e. the IsTypedBy inverse relationship is not provided, or the associated type object has to be of type IfcElementAssemblyType.
Inherited definitions from supertypes
Entity inheritance IfcElement IfcProduct IfcObject IfcObjectDefinition IfcRoot
Attribute inheritance
#AttributeTypeCardinalityDescriptionC
IfcRoot
1GlobalIdIfcGloballyUniqueId[1:1] Assignment of a globally unique identifier within the entire software world. X
2OwnerHistoryIfcOwnerHistory[0:1] 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 - either as addition, deletion or modification.
X
3NameIfcLabel[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
4DescriptionIfcText[0:1] Optional description, provided for exchanging informative comments.X
IfcObjectDefinition
HasAssignmentsIfcRelAssigns
@RelatedObjects		S[0:?]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.X
NestsIfcRelNests
@RelatedObjects		S[0:1]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). X
IsNestedByIfcRelNests
@RelatingObject		S[0:?]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). X
HasContextIfcRelDeclares
@RelatedDefinitions		S[0:1]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. X
IsDecomposedByIfcRelAggregates
@RelatingObject		S[0:?]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). X
DecomposesIfcRelAggregates
@RelatedObjects		S[0:1]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). X
HasAssociationsIfcRelAssociates
@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
5ObjectTypeIfcLabel[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
IsDeclaredByIfcRelDefinesByObject
@RelatedObjects		S[0:1]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. X
DeclaresIfcRelDefinesByObject
@RelatingObject		S[0:?]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. X
IsTypedByIfcRelDefinesByType
@RelatedObjects		S[0:1]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. X
IsDefinedByIfcRelDefinesByProperties
@RelatedObjects		S[0:?]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. X
IfcProduct
6ObjectPlacementIfcObjectPlacement[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
7RepresentationIfcProductRepresentation[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
ReferencedByIfcRelAssignsToProduct
@RelatingProduct		S[0:?]Reference to the IfcRelAssignsToProduct relationship, by which other products, processes, controls, resources or actors (as subtypes of IfcObjectDefinition) can be related to this product.X
IfcElement
8TagIfcIdentifier[0:1] 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.X
FillsVoidsIfcRelFillsElement
@RelatedBuildingElement		S[0:1]Reference to the IfcRelFillsElement Relationship that puts the element as a filling into the opening created within another element. X
ConnectedToIfcRelConnectsElements
@RelatingElement		S[0:?]Reference to the element connection relationship. The relationship then refers to the other element to which this element is connected to. X
IsInterferedByElementsIfcRelInterferesElements
@RelatedElement		S[0:?]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.
X
InterferesElementsIfcRelInterferesElements
@RelatingElement		S[0:?]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.
X
HasProjectionsIfcRelProjectsElement
@RelatingElement		S[0:?]Projection relationship that adds a feature (using a Boolean union) to the IfcBuildingElement.X
ReferencedInStructuresIfcRelReferencedInSpatialStructure
@RelatedElements		S[0:?]Reference relationship to the spatial structure element, to which the element is additionally associated. This relationship may not be hierarchical, an element may be referenced by zero, one or many spatial structure elements. X
HasOpeningsIfcRelVoidsElement
@RelatingBuildingElement		S[0:?]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. X
IsConnectionRealizationIfcRelConnectsWithRealizingElements
@RealizingElements		S[0:?]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. X
ProvidesBoundariesIfcRelSpaceBoundary
@RelatedBuildingElement		S[0:?]Reference to space boundaries by virtue of the objectified relationship IfcRelSpaceBoundary. It defines the concept of an element bounding spaces. X
ConnectedFromIfcRelConnectsElements
@RelatedElement		S[0:?]Reference to the element connection relationship. The relationship then refers to the other element that is connected to this element. X
ContainedInStructureIfcRelContainedInSpatialStructure
@RelatedElements		S[0:1]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. X
HasCoveringsIfcRelCoversBldgElements
@RelatingBuildingElement		S[0:?]Reference to IfcCovering by virtue of the objectified relationship IfcRelCoversBldgElement. It defines the concept of an element having coverings associated.X
IfcElementAssembly
9AssemblyPlaceIfcAssemblyPlaceEnum[0:1] A designation of where the assembly is intended to take place defined by an Enum.X
10PredefinedTypeIfcElementAssemblyTypeEnum[0:1] Predefined generic types for a element assembly that are specified in an enumeration. There might be property sets defined specifically for each predefined type. X
Definitions applying to Common Use Definitions

 Instance diagram

Concept usage

Object Typing

The Object Typing concept applies to this entity as shown in Table 46.

Type
IfcElementAssemblyType

Table 46 — IfcElementAssembly Object Typing



Aggregation

The Aggregation concept applies to this entity as shown in Table 47.

PredefinedTypeRelatedObjectsDescription
 IfcMemberMembers within the assembly.
 IfcPlatePlates within the assembly.
 IfcElementComponentComponents within the assembly.

Table 47 — IfcElementAssembly Aggregation

The IfcElementAssembly shall represent an aggregate, i.e. it should have other elements, being subtypes of IfcElement, as contained (sub)parts. The table above only represents a selection of subtypes of IfcElement that are legitimate as parts in an IfcElementAssembly

  • The IfcElementAssembly is an aggregate i.e. being composed by other elements and acting as an assembly using the objectified relationship IfcRelAggregates, refering to it by its inverse attribute SELF\IfcObjectDefinition.IsDecomposedBy. Components of an assembly are described by instances of subtypes of IfcElement.
  • In this case, the contained subtypes of IfcElement shall not be additionally contained in the project spatial hierarchy, i.e. the inverse attribute SELF\IfcElement.ContainedInStructure of those IfcElement's shall be NIL.

Figure 142 illustrates spatial containment and element aggregation relationships.

containment relationships

Figure 142 — Element assembly containment


Spatial Containment

The Spatial Containment concept applies to this entity as shown in Table 48.

StructureDescription
IfcBuildingStoreyDefault spatial container
IfcBuildingSpatial container for element assemblies not assignable to a building storey
IfcSiteSpatial container for element assemblies that are placed on site (outside of building)

Table 48 — IfcElementAssembly Spatial Containment

The IfcElementAssembly should have a relationship for its containment in the hierachical spatial structure of the project. Only if the IfcElementAssembly is itself a part of another assembly this relationship should be omitted.



Concept inheritance

#ConceptModel View
IfcRoot
Software IdentityCommon Use Definitions
Revision ControlCommon Use Definitions
IfcObject
Object Occurrence Predefined TypeCommon Use Definitions
IfcElement
Property Sets for ObjectsCommon Use Definitions
Product Local PlacementCommon Use Definitions
Box GeometryCommon Use Definitions
FootPrint GeometryCommon Use Definitions
Body SurfaceOrSolidModel GeometryCommon Use Definitions
Body SurfaceModel GeometryCommon Use Definitions
Body Tessellation GeometryCommon Use Definitions
Body Brep GeometryCommon Use Definitions
Body AdvancedBrep GeometryCommon Use Definitions
Body CSG GeometryCommon Use Definitions
Mapped GeometryCommon Use Definitions
Mesh GeometryCommon Use Definitions
IfcElementAssembly
Object TypingCommon Use Definitions
AggregationCommon Use Definitions
Spatial ContainmentCommon Use Definitions
Examples
Formal representations
XSD Specification
 <xs:element name="IfcElementAssembly" type="ifc:IfcElementAssembly" substitutionGroup="ifc:IfcElement" nillable="true"/>
 <xs:complexType name="IfcElementAssembly">
  <xs:complexContent>
   <xs:extension base="ifc:IfcElement">
    <xs:attribute name="AssemblyPlace" type="ifc:IfcAssemblyPlaceEnum" use="optional"/>
    <xs:attribute name="PredefinedType" type="ifc:IfcElementAssemblyTypeEnum" use="optional"/>
   </xs:extension>
  </xs:complexContent>
 </xs:complexType>
EXPRESS Specification
ENTITY IfcElementAssembly
 SUBTYPE OF (IfcElement);
  AssemblyPlace : OPTIONAL IfcAssemblyPlaceEnum;
  PredefinedType : OPTIONAL IfcElementAssemblyTypeEnum;
 WHERE
  CorrectPredefinedType : NOT(EXISTS(PredefinedType)) OR (PredefinedType <> IfcElementAssemblyTypeEnum.USERDEFINED) OR ((PredefinedType = IfcElementAssemblyTypeEnum.USERDEFINED) AND EXISTS (SELF\IfcObject.ObjectType));
  CorrectTypeAssigned : (SIZEOF(IsTypedBy) = 0) OR ('IFCPRODUCTEXTENSION.IFCELEMENTASSEMBLYTYPE' IN TYPEOF(SELF\IfcObject.IsTypedBy[1].RelatingType));
END_ENTITY;

Link to EXPRESS-G diagram EXPRESS-G diagram

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