8.18.3.12 IfcShapeAspect

Aspect de forme
Form - Aspekt

IfcShapeAspect allows for grouping of shape representation items that represent aspects (or components) of the shape of a product. Thereby shape representations of components of the product shape represent a distinctive part to a product that can be explicitly addressed.

The IfcShapeAspect's may have distinct material information or other distict characteristics that differs from other parts of the product shape representation.

NOTE  The IfcShapeAspect together with the IfcMaterialConstituent can be used to associate distict material information to parts of the product shape representation.

Figure 385 indicates the association of material characteristics to shape aspects.

shape

Figure 385 — shape aspects for associating material

NOTE  Definition from ISO 10303-41:
A shape aspect is an identifiable element of the shape of an object.
NOTE  Entity adapted from shape_aspect defined in ISO 10303-42.
HISTORY  New entity in IFC2.0
IFC4 CHANGE  Attribute PartOfProductDefinitionShape declared OPTIONAL and extended to type IfcProductRepresentationSelect with upward compatibility for file based exchange.

Informal Propositions:

  1. If ShapeRepresentations points to shape representations that are part of an IfcProductDefinitionShape, PartOfProductDefinitionShape must refer to this instance of IfcProductDefinitionShape.
  2. If ShapeRepresentations points to shape representations that are part of an IfcRepresentationMap, PartOfProductDefinitionShape must refer to this instance of IfcRepresentationMap.

XSD Specification:

 <xs:element name="IfcShapeAspect" type="ifc:IfcShapeAspect" substitutionGroup="ifc:Entity" nillable="true"/>
 <xs:complexType name="IfcShapeAspect">
  <xs:complexContent>
   <xs:extension base="ifc:Entity">
    <xs:sequence>
     <xs:element name="ShapeRepresentations">
      <xs:complexType>
       <xs:sequence>
        <xs:element ref="ifc:IfcShapeModel" maxOccurs="unbounded"/>
       </xs:sequence>
       <xs:attribute ref="ifc:itemType" fixed="ifc:IfcShapeModel"/>
       <xs:attribute ref="ifc:cType" fixed="list"/>
       <xs:attribute ref="ifc:arraySize" use="optional"/>
      </xs:complexType>
     </xs:element>
    </xs:sequence>
    <xs:attribute name="Name" type="ifc:IfcLabel" use="optional"/>
    <xs:attribute name="Description" type="ifc:IfcText" use="optional"/>
    <xs:attribute name="ProductDefinitional" type="ifc:logical" use="optional"/>
   </xs:extension>
  </xs:complexContent>
 </xs:complexType>

EXPRESS Specification:

ENTITY IfcShapeAspect;
ShapeRepresentations : LIST [1:?] OF IfcShapeModel;
Name : OPTIONAL IfcLabel;
Description : OPTIONAL IfcText;
ProductDefinitional : LOGICAL;
PartOfProductDefinitionShape : OPTIONAL IfcProductRepresentationSelect;
END_ENTITY;

Link to EXPRESS-G diagram EXPRESS-G diagram

Attribute Definitions:

ShapeRepresentations : List of shape representations. Each member defines a valid representation of a particular type within a particular representation context as being an aspect (or part) of a product definition.
IFC2x3 CHANGE  The data type has been changed from IfcShapeRepresentation to IfcShapeModel with upward compatibility
Name : The word or group of words by which the shape aspect is known. It is a tag to indicate the particular semantic of a component within the product definition shape, used to provide meaning. Example: use the tag "Glazing" to define which component of a window shape defines the glazing area.
Description : The word or group of words that characterize the shape aspect. It can be used to add additional meaning to the name of the aspect.
ProductDefinitional : An indication that the shape aspect is on the physical boundary of the product definition shape. If the value of this attribute is TRUE, it shall be asserted that the shape aspect being identified is on such a boundary. If the value is FALSE, it shall be asserted that the shape aspect being identified is not on such a boundary. If the value is UNKNOWN, it shall be asserted that it is not known whether or not the shape aspect being identified is on such a boundary. --- EXAMPLE: Would be FALSE for a center line, identified as shape aspect; would be TRUE for a cantilever. ---
PartOfProductDefinitionShape : Reference to the IfcProductDefinitionShape or the IfcRepresentationMap of which this shape is an aspect.
IFC4 CHANGE  Data type modified to be IfcProductRepresentationSelect allowing the assignment also to IfcRepresentationMap.

Inheritance Graph:

ENTITY IfcShapeAspect
ENTITY IfcShapeAspect
ShapeRepresentations : LIST [1:?] OF IfcShapeModel;
Name : OPTIONAL IfcLabel;
Description : OPTIONAL IfcText;
ProductDefinitional : LOGICAL;
PartOfProductDefinitionShape : OPTIONAL IfcProductRepresentationSelect;
END_ENTITY;

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