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IfcDiscreteElement

Definition from IAI: This class defines elements in a building services system that do not participate as either devices or distribution elements, such as insulation or attaching elements. This class will be more fully elaborated in future IFC releases.

HISTORY: New entity in IFC R2.0.
ISSUES: See issues and change log for changes made in IFC R2x.

Geometry Use Definitions

The geometric representation of IfcDiscreteElement is given by the IfcProductDefinitionShape, allowing multiple geometric representations. Included are:

Local Placement

The local placement is defined in the supertype IfcProduct. It is defined by a subtype of IfcObjectPlacement which can define an absolute placement, relative placement, or grid reference, with each defining the local coordinate system referenced by all geometric representations. The PlacementRelTo relationship of IfcLocalPlacement, if given, shall point to the same IfcSpatialStructureElement which is used in the ContainedInStructure inverse attribute, or to a referenced spatial structure element at a higher level. If the relative placement is not used, the absolute placement is defined within the world coordinate system.

Informal propositions for local placement:

  1. If the LocalPlacement is specified, then all aggregated components should use this placement as their relative placement.

Standard Geometric Representation

Currently, the use of attribute driven geometry for this class is not supported. The standard geometric representation is defined using explicit geometry.

B-Rep Representation

The faceted B-Rep capabilities (with or without voids) shall be supported for B-Rep representation.


EXPRESS specification:

ENTITY IfcDiscreteElement
SUBTYPE OF ( IfcEquipmentElement);
PredefinedType  :  IfcDiscreteElementTypeEnum;
WHERE
WR1  :  (PredefinedType <> IfcDiscreteElementTypeEnum.USERDEFINED) OR ((PredefinedType = IfcDiscreteElementTypeEnum.USERDEFINED) AND EXISTS(SELF\IfcObject.ObjectType));
END_ENTITY;

Attribute definitions:

PredefinedType  :  Predefined types for discrete elements are specified in an enumeration. There may be a property set given for the predefined types.

Formal Propositions:

WR1  :  ??

References (1):

Name Type Referred through Express-G
IfcEquipmentElement Entity
Subtype
Diagram 2

Inheritance graph

ENTITY IfcDiscreteElement;
ENTITY IfcRoot;
GlobalId  :  IfcGloballyUniqueId;
OwnerHistory  :  IfcOwnerHistory;
Name  :  OPTIONAL IfcLabel;
Description  :  OPTIONAL IfcText;
ENTITY IfcObject;
ObjectType  :  OPTIONAL IfcLabel;
INVERSE
IsDefinedBy  :  SET OF IfcRelDefines FOR RelatedObjects;
HasAssociations  :  SET OF IfcRelAssociates FOR RelatedObjects;
HasAssignments  :  SET OF IfcRelAssigns FOR RelatedObjects;
Decomposes  :  SET OF IfcRelDecomposes FOR RelatedObjects;
IsDecomposedBy  :  SET [0:1] OF IfcRelDecomposes FOR RelatingObject;
ENTITY IfcProduct;
ObjectPlacement  :  OPTIONAL IfcObjectPlacement;
Representation  :  OPTIONAL IfcProductRepresentation;
INVERSE
ReferencedBy  :  SET OF IfcRelAssignsToProduct FOR RelatingProduct;
ENTITY IfcElement;
Tag  :  OPTIONAL IfcIdentifier;
INVERSE
ConnectedTo  :  SET OF IfcRelConnectsElements FOR RelatingElement;
ConnectedFrom  :  SET OF IfcRelConnectsElements FOR RelatedElement;
ContainedInStructure  :  SET [0:1] OF IfcRelContainedInSpatialStructure FOR RelatedElements;
ENTITY IfcEquipmentElement;
ENTITY IfcDiscreteElement;
PredefinedType  :  IfcDiscreteElementTypeEnum;
END_ENTITY;