|Teil zu Ganzes Beziehung - Relation (allgemein)|
The decomposition relationship,
IfcRelDecomposes, defines the general concept of elements
being composed or decomposed. The decomposition relationship
denotes a whole/part hierarchy with the ability to navigate from
the whole (the composition) to the parts and vice versa.
Decompositions may be constrained by requiring both, the whole
and its parts, to be of the same type - thus establishing a
nesting relationship. Or they may require some form of physical
containment, thus establishing special types of aggregation
NOTE There are two special names for
decomposition, which are linguistically distinguished, nesting
and aggregation. The subtypes of IfcRelDecomposes will
introduce either the nesting or aggregation convention (see
IfcRelNests and IfcRelAggregates).
EXAMPLE A cost element is a nest of other cost
elements. Or a structural frame is an aggregation of beams and
columns. Both are applications of decomposition
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 decomposition relationship can
be applied in a recursive manner, i.e. a decomposed element can
be part in another decomposition. Cyclic references have to be
prevented at application level.
HISTORY New entity in IFC1.5, it is a generalisation of the IFC2.0 entity IfcRelNests.
IFC4 CHANGE The differentiation between the aggregation and nesting is determined to be a non-ordered or an ordered collection of parts. The attributes RelatingObject and RelatedObjects have been demoted to the subtypes.
XSD Specification: <xs:element name="IfcRelDecomposes" type="ifc:IfcRelDecomposes" abstract="true" substitutionGroup="ifc:IfcRelationship" nillable="true"/>
<xs:complexType name="IfcRelDecomposes" abstract="true">
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