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Definition from ISO/CD 10303-43:1992: A mapped item is the use of an existing representation (the mapping source - mapped representation) as a representation item in a second representation.

NOTE: A mapped item is a subtype of representation item. It enables a representation to be used as a representation item in one or more other representations. The mapped item allows for the definition of a representation using other representations.

Definition from IAI: The IfcMappedItem is the inserted instance of a source definition (to be compared with a block / shared cell / macro definition). The instance is inserted by applying a Cartesian transformation operator as the MappingTarget.

EXAMPLE  An IfcMappedItem can reuse other mapped items (ako nested blocks), doing so the IfcRepresentationMap is based on an IfcShapeRepresentation including one or more IfcMappedItem's.

NOTE   Corresponding STEP entity: mapped_item. Please refer to ISO/IS 10303-43:1994, for the final definition of the formal standard. The definition of mapping_target (MappingTarget) has been restricted to be of the type cartesian_transformation_operator (IfcCartesianTransformationOperator).

HISTORY  New entity in IFC Release 2x.

Informal Propositions

  1. A mapped item shall not be self-defining by participating in the definition of the representation being mapped.
  2. The dimensionality of the mapping source and the mapping target has to be the same, if the mapping source is a geometric representation item.

EXPRESS specification:

ENTITY IfcMappedItem
SUBTYPE OF ( IfcRepresentationItem);
MappingSource  :  IfcRepresentationMap;
MappingTarget  :  IfcCartesianTransformationOperator;

Attribute definitions:

MappingSource  :  A representation map that is the source of the mapped item. It can be seen as a block (or cell or marco) definition.
MappingTarget  :  A representation item that is the target onto which the mapping source is mapped. It is constraint to be a Cartesian transformation operator.

Inheritance graph

ENTITY IfcMappedItem;
ENTITY IfcRepresentationItem;
LayerAssignments  :  SET OF IfcPresentationLayerAssignment FOR AssignedItems;
StyledByItem  :  SET [0:1] OF IfcStyledItem FOR Item;
ENTITY IfcMappedItem;
MappingSource  :  IfcRepresentationMap;
MappingTarget  :  IfcCartesianTransformationOperator;