5.1.3.37 IfcRelDefinesByObject

5.1.3.37.1 Semantic definition

The objectified relationship IfcRelDefinesByObject defines the relationship between an object that is part in an object type decomposition and an object occurrence that is 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 one or many reflected objects. Those objects then share the same object property sets and, for subtypes of IfcProduct, the eventually assigned representation maps.

The relationship IfcRelDefinesByObject may only connect objects that take part in both a type decomposition and an occurrence decomposition of the same type. 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.

instance diagram — Figure 5.1.3.37.A — Part definition relationships

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.

geometry diagram — Figure 5.1.3.37.B — Part definition relationships with shape representation

5.1.3.37.2 Entity inheritance

- IfcRoot

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. NOTE Only the last modification is stored - either as addition, deletion or modification. IFC4-CHANGE The attribute has been changed to be OPTIONAL.
3	Name	OPTIONAL IfcLabel	An 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	An optional description, provided to exchange informative comments.
Click to show 4 hidden inherited attributes Click to hide 4 inherited attributes
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.

Table 5.1.3.37.C

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 also provide a name and description for the concept.
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Table 5.1.3.37.D

5.1.3.37.5 Formal representation

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