IfcObjectDefinition

Natural language names
Objektdefinition
Object Definition
Définition d'objet
Semantic definitions at the entity
Entity definition

An IfcObjectDefinition is the generalization of any semantically treated thing or process, either being a type or an occurrences. Object defintions can be named, using the inherited Name attribute, which should be a user recognizable label for the object occurrance. Further explanations to the object can be given using the inherited Description attribute. A context is a specific kind of object definition as it provides the project or library context in which object types and object occurrences are defined.

Objects are independent pieces of information that might contain or reference other pieces of information. There are four essential kinds of relationships in which object definitons (by their instantiable subtypes) can be involved:

NOTE  The link between the uppermost object in the spatial structure tree, that is IfcSite or ifcBuilding, and the context provided by IfcProject is created using the IfcRelAggregates relationship. See IfcProject for more information.

HISTORY  New abstract entity in IFC2x3.

IFC4 CHANGE The new subtype IfcContext and the relationship to context HasContext has been added . The decomposition relationship is split into ordered nesting (Nests, IsNestedBy) and un-ordered aggregating (Decomposes, IsDecomposedBy).

Attribute definitions
#AttributeTypeCardinalityDescription G
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).
IFC4 CHANGE  The inverse attribute datatype has been added and separated from Decomposes defined at IfcObjectDefinition.
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).
IFC4 CHANGE  The inverse attribute datatype has been added and separated from IsDecomposedBy defined at IfcObjectDefinition.
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.
IFC4 CHANGE  The inverse attribute datatype has been added.
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).
IFC4 CHANGE  The inverse attribute datatype has been changed from the supertype IfcRelDecomposes to subtype IfcRelAggregates.
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).
IFC4 CHANGE  The inverse attribute datatype has been changed from the supertype IfcRelDecomposes to subtype IfcRelAggregates.
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
Inherited definitions from supertypes
Entity inheritance IfcContext IfcObject IfcTypeObject IfcRoot
Attribute inheritance
#AttributeTypeCardinalityDescriptionG
IfcRoot
1GlobalIdIfcGloballyUniqueId Assignment of a globally unique identifier within the entire software world. X
2OwnerHistoryIfcOwnerHistory? 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.
X
3NameIfcLabel? 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? 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).
IFC4 CHANGE  The inverse attribute datatype has been added and separated from Decomposes defined at IfcObjectDefinition.
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).
IFC4 CHANGE  The inverse attribute datatype has been added and separated from IsDecomposedBy defined at IfcObjectDefinition.
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.
IFC4 CHANGE  The inverse attribute datatype has been added.
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).
IFC4 CHANGE  The inverse attribute datatype has been changed from the supertype IfcRelDecomposes to subtype IfcRelAggregates.
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).
IFC4 CHANGE  The inverse attribute datatype has been changed from the supertype IfcRelDecomposes to subtype IfcRelAggregates.
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
Definitions applying to General Usage

 Instance diagram


Concept usage

Classification Association

The Classification Association concept applies to this entity.

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.



mvdXML Specification
<?xml version="1.0" encoding="utf-8"?>
<ConceptRoot xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" uuid="f26454ea-55a9-4d8f-a2a0-ab8a5561112d" name="IfcObjectDefinition" applicableRootEntity="IfcObjectDefinition">
 <Applicability>
  <Template ref="95f14c0b-d81c-49cb-be71-edd4e4eb395c" />
  <TemplateRules operator="and">
  </TemplateRules>
 </Applicability>
 <Concepts>
  <Concept uuid="dcfad64e-cedb-4766-b609-cfe82ae3ae44" name="Classification Association">
   <Template ref="4a224609-6578-4c75-afcf-8affa86e5ef2" />
  </Concept>
 </Concepts>
</ConceptRoot>
Concept inheritance

#ConceptTemplateModel View
IfcRoot
IdentitySoftware IdentityGeneral Usage
Revision ControlRevision ControlGeneral Usage
IfcObjectDefinition
Classification AssociationClassification AssociationGeneral Usage
Formal representations
XML Specification
 <xs:element name="IfcObjectDefinition" type="ifc:IfcObjectDefinition" abstract="true" substitutionGroup="ifc:IfcRoot" nillable="true"/>
 <xs:complexType name="IfcObjectDefinition" abstract="true">
  <xs:complexContent>
   <xs:extension base="ifc:IfcRoot">
    <xs:sequence>
     <xs:element name="IsNestedBy" nillable="true" minOccurs="0">
      <xs:complexType>
       <xs:sequence>
        <xs:element ref="ifc:IfcRelNests" minOccurs="0" maxOccurs="unbounded"/>
       </xs:sequence>
       <xs:attribute ref="ifc:itemType" fixed="ifc:IfcRelNests"/>
       <xs:attribute ref="ifc:cType" fixed="set"/>
       <xs:attribute ref="ifc:arraySize" use="optional"/>
      </xs:complexType>
     </xs:element>
     <xs:element name="IsDecomposedBy" nillable="true" minOccurs="0">
      <xs:complexType>
       <xs:sequence>
        <xs:element ref="ifc:IfcRelAggregates" minOccurs="0" maxOccurs="unbounded"/>
       </xs:sequence>
       <xs:attribute ref="ifc:itemType" fixed="ifc:IfcRelAggregates"/>
       <xs:attribute ref="ifc:cType" fixed="set"/>
       <xs:attribute ref="ifc:arraySize" use="optional"/>
      </xs:complexType>
     </xs:element>
    </xs:sequence>
   </xs:extension>
  </xs:complexContent>
 </xs:complexType>
EXPRESS Specification
ENTITY IfcObjectDefinition
 ABSTRACT SUPERTYPE OF(ONEOF(IfcContext, IfcObject, IfcTypeObject))
 SUBTYPE OF (IfcRoot);
 INVERSE
  HasAssignments : SET [0:?] OF IfcRelAssigns FOR RelatedObjects;
  Nests : SET [0:1] OF IfcRelNests FOR RelatedObjects;
  IsNestedBy : SET [0:?] OF IfcRelNests FOR RelatingObject;
  HasContext : SET [0:1] OF IfcRelDeclares FOR RelatedDefinitions;
  IsDecomposedBy : SET [0:?] OF IfcRelAggregates FOR RelatingObject;
  Decomposes : SET [0:1] OF IfcRelAggregates FOR RelatedObjects;
  HasAssociations : SET [0:?] OF IfcRelAssociates FOR RelatedObjects;
END_ENTITY;

Link to EXPRESS-G diagram EXPRESS-G diagram

References  References: IfcRelAggregates IfcRelAssigns IfcRelDefinesByProperties IfcRelNests IfcDefinitionSelect

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