IfcRelNests

Item	Change	Description
IFC2x3 to IFC4
IfcRelNests
OwnerHistory	MODIFIED	Instantiation changed to OPTIONAL.
RelatedObjects	MODIFIED	Aggregation changed from SET to LIST.

Semantic definitions at the entity

Entity 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.

EXAMPLE A nesting of costs items in an IfcCostSchedule is the composition of complex cost items from other cost items. The order of the nested cost items underneath the parent cost item is determined by the order of the list of RelatedObjects.

EXAMPLE A nesting of IfcTask's within a work schedule is the composition of a parent work task from more specific sub work tasks. The order of the sub tasks underneath the parent task is determined by the order of the list of RelatedObjects.

EXAMPLE A series of IfcDistributionPort's can be nested within an IfcDistributionElement. They decompose the distribution element and have an implied order.

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.

HISTORY New entity in IFC2.0

IFC4 CHANGE The attributes RelatingObject and RelatedObjects are demoted from the supertype IfcRelDecomposes, and RelatedObjects is refined to be a list. The use of IfcRelNests is repurposed to be a nesting of an ordered collections of parts.

Attribute definitions

#	Attribute	Type	Cardinality	Description	C
5	RelatingObject	IfcObjectDefinition	[1:1]	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.	X
6	RelatedObjects	IfcObjectDefinition	L[1:?]	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.	X

Formal Propositions

Rule	Description
NoSelfReference	The instance to with the relation points as provided by RelatingObject shall not be contained in the list of RelatedObjects.

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	C
IfcRoot
1	GlobalId	IfcGloballyUniqueId	[1:1]	Assignment of a globally unique identifier within the entire software world.	X
2	OwnerHistory	IfcOwnerHistory	[0:1]	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.	X
3	Name	IfcLabel	[0:1]	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
4	Description	IfcText	[0:1]	Optional description, provided for exchanging informative comments.	X
IfcRelationship
IfcRelDecomposes
IfcRelNests
5	RelatingObject	IfcObjectDefinition	[1:1]	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.	X
6	RelatedObjects	IfcObjectDefinition	L[1:?]	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.	X

Definitions applying to Common Use Definitions

Concept inheritance

#	Concept	Model View
IfcRoot
	Software Identity	Common Use Definitions
	Revision Control	Common Use Definitions

Examples

Air terminal element

Formal representations

XSD Specification

 <xs:element name="IfcRelNests" type="ifc:IfcRelNests" substitutionGroup="ifc:IfcRelDecomposes" nillable="true"/>

 <xs:complexType name="IfcRelNests">

  <xs:complexContent>

   <xs:extension base="ifc:IfcRelDecomposes">

    <xs:sequence>

     <xs:element name="RelatedObjects">

      <xs:complexType>

       <xs:sequence>

        <xs:element ref="ifc:IfcObjectDefinition" maxOccurs="unbounded"/>

       </xs:sequence>

       <xs:attribute ref="ifc:itemType" fixed="ifc:IfcObjectDefinition"/>

       <xs:attribute ref="ifc:cType" fixed="list"/>

       <xs:attribute ref="ifc:arraySize" use="optional"/>

      </xs:complexType>

     </xs:element>

    </xs:sequence>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcRelNests

 SUBTYPE OF (IfcRelDecomposes);

  RelatingObject : IfcObjectDefinition;

  RelatedObjects : LIST [1:?] OF IfcObjectDefinition;

 WHERE

  NoSelfReference : SIZEOF(QUERY(Temp <* RelatedObjects | RelatingObject :=: Temp)) = 0;
END_ENTITY;

 EXPRESS-G diagram

Link to this page

	Teil zu Ganzes Beziehung geordnet - Relation
	Rel Nests