5.1.3.41 IfcRelNests

5.1.3.41.1 Semantic definition

The nesting relationship IfcRelNests is a special type of the general composition/decomposition (or whole/part) relationship IfcRelDecomposes. The nesting relationship can be applied to all non physical subtypes of object and object types, namely processes, controls (like cost items), and resources. It can also be applied to physical subtypes of object and object types, namely elements having ports. The nesting implies an order among the nested parts.

Decompositions imply a dependency, i.e. the definition of the whole depends on the definition of the parts and the parts depend on the existence of the whole. The behaviour that is implied from the dependency has to be established inside the applications.

5.1.3.41.2 Entity inheritance

- IfcRoot

5.1.3.41.3 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 in stored - either as addition, deletion or modification. IFC4-CHANGE The attribute has been changed to be OPTIONAL.
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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IfcRelNests (2)
5	RelatingObject	IfcObjectDefinition	The object definition, either an non-product object type or a non-product object occurrence, that represents the nest. It is the whole within the whole/part relationship. IFC4-CHANGE The attribute has been demoted from the supertype IfcRelDecomposes and defines the ordered nesting relationship.
6	RelatedObjects	LIST [1:?] OF IfcObjectDefinition	The object definitions, either non-product object occurrences or non-product object types, that are being nestes. They are defined as the parts in the ordered whole/part relationship - i.e. there is an implied order among the parts expressed by the position within the list of RelatedObjects. IFC4-CHANGE The attribute has been demoted from the supertype IfcRelDecomposes and defines the ordered set of parts within the nest.

Table 5.1.3.41.A

5.1.3.41.4 Formal propositions

Name	Description
NoSelfReference	The instance to with the relation points as provided by RelatingObject shall not be contained in the list of RelatedObjects.
`SIZEOF(QUERY(Temp <* RelatedObjects \| RelatingObject :=: Temp)) = 0`

Table 5.1.3.41.B

5.1.3.41.5 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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Table 5.1.3.41.C

5.1.3.41.6 Formal representation

ENTITY IfcRelNests
 SUBTYPE OF (IfcRelDecomposes);
	RelatingObject : IfcObjectDefinition;
	RelatedObjects : LIST [1:?] OF IfcObjectDefinition;
 WHERE
	NoSelfReference : SIZEOF(QUERY(Temp <* RelatedObjects | RelatingObject :=: Temp)) = 0;
END_ENTITY;