8.18.3.10 IfcRepresentation

Représentation
Repräsentation

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 andRepresentationMap 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:

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.

XSD 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 OF IfcPresentationLayerAssignment FOR AssignedItems;
OfProductRepresentation : SET OF IfcProductRepresentation FOR Representations;
END_ENTITY;

Link to EXPRESS-G diagram EXPRESS-G diagram

Attribute Definitions:

ContextOfItems : Definition of the representation context for which the different subtypes of representation are valid.
RepresentationIdentifier : The optional identifier of the representation as used within a project.
RepresentationType : 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.
Items : Set of geometric representation items that are defined for this representation.
RepresentationMap : 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 : 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 : 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.

Inheritance Graph:

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

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