8.18.3.20 IfcTopologyRepresentation

8.18.3.20.1 Semantic 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:

Type	Description
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

Table 8.18.3.20.B

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

8.18.3.20.2 Entity inheritance

8.18.3.20.3 Attributes

#	Attribute	Type	Description
IfcRepresentation (7)
1	ContextOfItems	IfcRepresentationContext	Definition of the representation context for which the different subtypes of representation are valid.
2	RepresentationIdentifier	OPTIONAL IfcLabel	The optional identifier of the representation as used within a project.
3	RepresentationType	OPTIONAL IfcLabel	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.
4	Items	SET [1:?] OF IfcRepresentationItem	Set of geometric representation items that are defined for this representation.
	RepresentationMap	SET [0:1] OF IfcRepresentationMap FOR MappedRepresentation	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
	LayerAssignments	SET [0:?] OF IfcPresentationLayerAssignment FOR AssignedItems	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
	OfProductRepresentation	SET [0:?] OF IfcProductRepresentation FOR Representations	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.
Click to show 7 hidden inherited attributes
IfcShapeModel (1)
	OfShapeAspect	SET [0:1] OF IfcShapeAspect FOR ShapeRepresentations	Reference to the shape aspect, for which it is the shape representation.

Table 8.18.3.20.C

8.18.3.20.4 Formal propositions

Name Description

WR21

Only topological representation items should be used.

 SIZEOF(QUERY(temp <* SELF\IfcRepresentation.Items | 
  NOT('IFC4X3_DEV_738df036.IFCTOPOLOGICALREPRESENTATIONITEM' IN TYPEOF(temp))
)) = 0

WR22

A representation type should be given to the topology representation.

EXISTS(SELF\IfcRepresentation.RepresentationType)

WR23

Checks the proper use of Items according to the RepresentationType.

IfcTopologyRepresentationTypes(SELF\IfcRepresentation.RepresentationType, SELF\IfcRepresentation.Items)

Table 8.18.3.20.D

8.18.3.20.5 Examples

Figure 8.18.3.20.A

Structural Curve Member

8.18.3.20.6 Formal representation

 ENTITY IfcTopologyRepresentation
 SUBTYPE OF (IfcShapeModel);
 WHERE
	WR21 : SIZEOF(QUERY(temp <* SELF\IfcRepresentation.Items | 
  NOT('IFC4X3_DEV_738df036.IFCTOPOLOGICALREPRESENTATIONITEM' IN TYPEOF(temp))
)) = 0
 
;
	WR22 : EXISTS(SELF\IfcRepresentation.RepresentationType);
	WR23 : IfcTopologyRepresentationTypes(SELF\IfcRepresentation.RepresentationType, SELF\IfcRepresentation.Items);
END_ENTITY;

8.18.3.20.7 References

IfcShapeModel

	ENTITY IfcTopologyRepresentation
	SUBTYPE OF (IfcShapeModel);
	WHERE
	WR21 : SIZEOF(QUERY(temp <* SELF\IfcRepresentation.Items \|
	NOT('IFC4X3_DEV_738df036.IFCTOPOLOGICALREPRESENTATIONITEM' IN TYPEOF(temp))
	)) = 0

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