IfcRepresentation

Item	Change	Description
IFC2x3 to IFC4 4.0.0.0
IfcRepresentation	MODIFIED	Instantiation changed to ABSTRACT.
IFC2x3 to IFC4 4.0.0.0
IfcRepresentation	MODIFIED	Instantiation changed to ABSTRACT.

Semantic definitions at the entity

Entity definition

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.

Attribute definitions

#	Attribute	Type	Cardinality	Description	G
1	ContextOfItems	IfcRepresentationContext		Definition of the representation context for which the different subtypes of representation are valid.	X
2	RepresentationIdentifier	IfcLabel	?	The optional identifier of the representation as used within a project.	X
3	RepresentationType	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.	X
4	Items	IfcRepresentationItem	S[1:?]	Set of geometric representation items that are defined for this representation.	X
	RepresentationMap	IfcRepresentationMap @MappedRepresentation	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	X
	LayerAssignments	IfcPresentationLayerAssignment @AssignedItems	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	X
	OfProductRepresentation	IfcProductRepresentation @Representations	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.	X

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	G
IfcRepresentation
1	ContextOfItems	IfcRepresentationContext		Definition of the representation context for which the different subtypes of representation are valid.	X
2	RepresentationIdentifier	IfcLabel	?	The optional identifier of the representation as used within a project.	X
3	RepresentationType	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.	X
4	Items	IfcRepresentationItem	S[1:?]	Set of geometric representation items that are defined for this representation.	X
	RepresentationMap	IfcRepresentationMap @MappedRepresentation	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	X
	LayerAssignments	IfcPresentationLayerAssignment @AssignedItems	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	X
	OfProductRepresentation	IfcProductRepresentation @Representations	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.	X

Formal representations

XML Specification

 <xs:element name="IfcRepresentation" type="ifc:IfcRepresentation" abstract="true" substitutionGroup="ifc:Entity" nillable="true"/>

 <xs:complexType name="IfcRepresentation" abstract="true">

  <xs:complexContent>

   <xs:extension base="ifc:Entity">

    <xs:sequence>

     <xs:element name="ContextOfItems" type="ifc:IfcRepresentationContext" nillable="true"/>

     <xs:element name="Items">

      <xs:complexType>

       <xs:sequence>

        <xs:element ref="ifc:IfcRepresentationItem" maxOccurs="unbounded"/>

       </xs:sequence>

       <xs:attribute ref="ifc:itemType" fixed="ifc:IfcRepresentationItem"/>

       <xs:attribute ref="ifc:cType" fixed="set"/>

       <xs:attribute ref="ifc:arraySize" use="optional"/>

      </xs:complexType>

     </xs:element>

    </xs:sequence>

    <xs:attribute name="RepresentationIdentifier" type="ifc:IfcLabel" use="optional"/>

    <xs:attribute name="RepresentationType" type="ifc:IfcLabel" use="optional"/>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcRepresentation

 ABSTRACT SUPERTYPE OF(ONEOF(IfcShapeModel, IfcStyleModel));

  ContextOfItems : IfcRepresentationContext;

  RepresentationIdentifier : OPTIONAL IfcLabel;

  RepresentationType : OPTIONAL IfcLabel;

  Items : SET [1:?] OF IfcRepresentationItem;

 INVERSE

  RepresentationMap : SET [0:1] OF IfcRepresentationMap FOR MappedRepresentation;

  LayerAssignments : SET [0:?] OF IfcPresentationLayerAssignment FOR AssignedItems;

  OfProductRepresentation : SET [0:?] OF IfcProductRepresentation FOR Representations;

END_ENTITY;

 EXPRESS-G diagram

	Repräsentation
	Representation
	Représentation