5.1.3.37 IfcRelDefinesByObject

5.1.3.37.1 Semantic definition

The objectified relationship IfcRelDefinesByObject defines the relationship between an object taking part in an object type decomposition and an object occurrence taking part in an occurrence decomposition of that type.

The IfcRelDefinesByObject is a 1-to-N relationship, as it allows for the assignment of one declaring object information to a single or to many reflected objects. Those objects then share the same object property sets and, for subtypes of IfcProduct, the eventually assigned representation maps.

Only objects that take part in a type decomposition and in an occurrence decomposition of the same type can be connected by the IfcRelDefinesByObject relationship. The IfcRelDefinesByObject links the decomposed object type part, also called the "declaring part" with the occurrence of that part inside the occurrence of the decomposed type, also called the "reflected part", as shown in Figure 5.1.3.37.A.

The IfcRelDefinesByObject can be used together with the shape representations of the product type as shown in Figure 5.1.3.37.B. The IfcShapeRepresentation of the "declaring part" is referenced by the "reflected part". The IfcObjectPlacement of the model occurrence (the whole) determines the position within the project context.

5.1.3.37.2 Entity inheritance

1. • IfcRoot
2. • IfcRelationship
   • IfcObjectDefinition
   • IfcPropertyDefinition
3. • IfcRelDefines
   • IfcRelAssigns
   • IfcRelAssociates
   • IfcRelConnects
   • IfcRelDeclares
   • IfcRelDecomposes
4. • IfcRelDefinesByObject
   • IfcRelDefinesByProperties
   • IfcRelDefinesByTemplate
   • IfcRelDefinesByType

5.1.3.37.3 Attributes

#	Attribute	Type	Description
IfcRoot (4)
1	GlobalId	IfcGloballyUniqueId	Assignment of a globally unique identifier within the entire software world.
2	OwnerHistory	OPTIONAL IfcOwnerHistory	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,
3	Name	OPTIONAL IfcLabel	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.
4	Description	OPTIONAL IfcText	Optional description, provided for exchanging informative comments.
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IfcRelDefinesByObject (2)
5	RelatedObjects	SET [1:?] OF IfcObject	Objects being part of an object occurrence decomposition, acting as the "reflecting parts" in the relationship.
6	RelatingObject	IfcObject	Object being part of an object type decomposition, acting as the "declaring part" in the relationship.

5.1.3.37.4 Concept usage

Concept	Usage	Description
IfcRoot (2)
Revision Control	General	Ownership, history, and merge state is captured using IfcOwnerHistory.
Software Identity	General	IfcRoot assigns the globally unique ID. In addition it may provide for a name and a description about the concept.
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5.1.3.37.5 Formal representation

ENTITY IfcRelDefinesByObject
 SUBTYPE OF (IfcRelDefines);
	RelatedObjects : SET [1:?] OF IfcObject;
	RelatingObject : IfcObject;
END_ENTITY;

5.1.3.37.6 References

• IfcObject
• IfcRelDefines