IFC (IFC4X3) development IfcRelNests 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. Entity inheritance 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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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.

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.

Table Formal propositions

Name Description

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 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 Formal representation

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

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  • attribute, RelatedObjects
  • attribute, RelatingObject
  • where rule, NoSelfReference
  • where rule, WR1