IFC 4.3.x development IfcRepresentation

Change log


modificationsabstractChanged from False to True Semantic definitions at the entity

The IfcRepresentation defines the general concept of representing product properties and in particular the product shape.

NOTE  Definition from ISO 10303-43:
A representation is a collection of one or more representation items that are related in a specified representation context. The relationship of representation item to representation context is the basis for distinguishing which representation item entities are related.

A representation item can be related to a representation context directly, when it occurs as an element is a representation, or indirectly, when it is referenced through any number of intervening entities, each of type representation item.

NOTE  Entity adapted from representation defined in ISO 10303-42.

HISTORY  New entity in IFC2.0

IFC2x3 CHANGE  The inverse attributes LayerAssignments and_RepresentationMap_ have been added with upward compatibility.

IFC4 CHANGE  Entity IfcRepresentation has been changed into an ABSTRACT supertype.

Representation Use Definition

Each representation, either IfcShapeRepresentation, or IfcTopologyRepresentation shall have a well defined:

  • ContextOfItems: Reference to an IfcGeometricRepresentationContext as agreed for this representation.
  • RepresentationIdentifier: Name of the representation, for example, 'Body' for 3D shape, 'FootPrint' for 2D ground view, 'Axis' for reference axis.
  • RepresentationType: Name for the geometric, or topological representation type, for example, 'SweptSolid' for 3D swept solids, 'Brep' for boundary representation.

NOTE  Guidelines for applying correct values to those attributes are provided in the geometry use definition section at each subtype of IfcElement. These guidelines can be further refined in view definitions or implementer agreements. Attributes

# Attribute Type Description
1 ContextOfItems IfcRepresentationContext Definition of the representation context for which the different subtypes of representation are valid.
2 RepresentationIdentifierOPTIONAL 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 AssignedItemsAssignment 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. Entity inheritance

dot_inheritance IfcShapeModel IfcShapeModel IfcRepresentation IfcRepresentation IfcShapeModel->IfcRepresentation IfcStyleModel IfcStyleModel IfcStyleModel->IfcRepresentation Formal representations

ENTITY IfcRepresentation
	ContextOfItems : IfcRepresentationContext;
	RepresentationIdentifier : OPTIONAL IfcLabel;
	RepresentationType : OPTIONAL IfcLabel;
	Items : SET [1:?] OF IfcRepresentationItem;
	RepresentationMap : SET [0:1] OF IfcRepresentationMap FOR MappedRepresentation;
	LayerAssignments : SET [0:?] OF IfcPresentationLayerAssignment FOR AssignedItems;
	OfProductRepresentation : SET [0:?] OF IfcProductRepresentation FOR Representations;