IFC 4.3.1.0 (IFC4X3_ADD1)

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.A

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.

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.

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.

Click to show 7 hidden inherited attributes Click to hide 7 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.B

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_ADD1.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.C

8.18.3.20.5 Formal representation

ENTITY IfcTopologyRepresentation
 SUBTYPE OF (IfcShapeModel);
 WHERE
	WR21 : SIZEOF(QUERY(temp <* SELF\IfcRepresentation.Items | 
  NOT('IFC4X3_ADD1.IFCTOPOLOGICALREPRESENTATIONITEM' IN TYPEOF(temp))
)) = 0

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

8.18.3.20.6 References