Natural language names
Topologische Repräsentation
Topology Representation
Représentation topologique
Semantic definitions at the entity
Entity definition

IfcTopologyRepresentation represents the concept of a particular topological representation of a product or a product component within a representation context. This representation context does not need to be (but may be) a geometric representation context. Several representation types for shape representation are included as predefined types:

Vertex topological vertex representation (with or without assigned geometry)
Edge topological edge representation (with or without assigned geometry)
Path topological path representation (with or without assigned geometry)
Face topological face representation (with or without assigned geometry)
Shell topological shell representation (with or without assigned geometry)
Undefined no constraints imposed

The representation type is given as a string value at the inherited attribute 'RepresentationType'.

HISTORY  New entity in IFC2x2.
Formal Propositions
WR21Only topological representation items should be used.
WR22A representation type should be given to the topology representation.
WR23Checks the proper use of Items according to the RepresentationType.
Inherited definitions from supertypes
Entity inheritance IfcShapeModel IfcRepresentation
Attribute inheritance
1ContextOfItemsIfcRepresentationContext Definition of the representation context for which the different subtypes of representation are valid.X
2RepresentationIdentifierIfcLabel? The optional identifier of the representation as used within a project.X
3RepresentationTypeIfcLabel? The description of the type of a representation context. The representation type defines the type of geometry or topology used for representing the product representation. More information is given at the subtypes IfcShapeRepresentation and IfcTopologyRepresentation.
The supported values for context type are to be specified by implementers agreements.
4ItemsIfcRepresentationItemS[1:?] Set of geometric representation items that are defined for this representation.X
S[0:1]Use of the representation within an IfcRepresentationMap. If used, this IfcRepresentation may be assigned to many representations as one of its Items using an IfcMappedItem. Using IfcRepresentationMap is the way to share one representation (often of type IfcShapeRepresentation) by many products.
IFC2x3 CHANGE  The inverse attribute LayerAssignments has been added
S[0:?]Assignment of the whole representation to a single or multiple layer(s). The LayerAssigments can be overridden by LayerAssigments of the IfcRepresentationItem's within the list of Items.
NOTE  Implementation agreements can restrict the maximum number of layer assignments to 1.
IFC2x3 CHANGE  The inverse attribute LayerAssignments has been added
S[0:?]Reference to the product representations to which this individual representation applies. In most cases it is the reference to one or many product shapes, to which this shape representation is applicable.
IFC4 CHANGE Inverse relationship cardinality relaxed to be 0:N.
S[0:1]Reference to the shape aspect, for which it is the shape representation.X
Formal representations
XML Specification
 <xs:element name="IfcTopologyRepresentation" type="ifc:IfcTopologyRepresentation" substitutionGroup="ifc:IfcShapeModel" nillable="true"/>
 <xs:complexType name="IfcTopologyRepresentation">
   <xs:extension base="ifc:IfcShapeModel"/>
EXPRESS Specification
ENTITY IfcTopologyRepresentation
 SUBTYPE OF (IfcShapeModel);
  WR21 : SIZEOF(QUERY(temp <* SELF\IfcRepresentation.Items |
NOT('IFCTOPOLOGYRESOURCE.IfcTopologicalRepresentationItem' IN TYPEOF(temp))
)) = 0

  WR22 : EXISTS(SELF\IfcRepresentation.RepresentationType);
  WR23 : IfcTopologyRepresentationTypes(SELF\IfcRepresentation.RepresentationType, SELF\IfcRepresentation.Items);

Link to EXPRESS-G diagram EXPRESS-G diagram

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