IFC 4.3.x development IfcRelDefinesByObject

Change log


added Semantic definitions at the entity

The objectified relationship IfcRelDefinesByObject defines the relationship between an object taking part in an object type decomposition and an object occurrences taking part in an occurrence decomposition of that type.

The IfcRelDefinesByObject is a 1-to-N relationship, as it allows for the assignment of one declaring object information to a single or to many reflected objects. Those objects then share the same object property sets and, for subtypes of IfcProduct, the eventually assigned representation maps.

Only objects that take part in a type decomposition and in an occurrence decomposition of the same type can be connected by the IfcRelDefinesByObject relationship. The IfcRelDefinesByObject links the decomposed object type part, also called the "declaring part" with the occurrence of that part inside the occurrence of the decomposed type, also called the "reflected part", as shown in Figure 1.


"instance diagram"

The IfcRelDefinesByObject can be used together with the shape representations of the product type as shown in Figure 2. The IfcShapeRepresentation of the "declaring part" is referenced by the "reflected part". The IfcObjectPlacement of the model occurrence (the whole) determines the position within the project context.

"geometry diagram"

HISTORY  New entity in IFC4. Attributes

#Attribute Type Description
1GlobalId IfcGloballyUniqueId Assignment of a globally unique identifier within the entire software world.
2OwnerHistory OPTIONAL IfcOwnerHistoryAssignment of the information about the current ownership of that object, including owning actor, application, local identification and information captured about the recent changes of the object,

> NOTE  only the last modification in stored - either as addition, deletion or modification.

> IFC4 CHANGE  The attribute has been changed to be OPTIONAL.
3Name OPTIONAL IfcLabel Optional name for use by the participating software systems or users. For some subtypes of IfcRoot the insertion of the Name attribute may be required. This would be enforced by a where rule.
4Description OPTIONAL IfcText Optional description, provided for exchanging informative comments.
5RelatedObjectsSET [1:?] OF IfcObject Objects being part of an object occurrence decomposition, acting as the "reflecting parts" in the relationship.
6RelatingObjectIfcObject Object being part of an object type decomposition, acting as the "declaring part" in the relationship. Entity inheritance

dot_inheritance IfcRelDefinesByObject IfcRelDefinesByObject IfcRelDefines IfcRelDefines IfcRelDefinesByObject->IfcRelDefines IfcRelDefines_children 3 more... IfcRelDefines_children->IfcRelDefines IfcRelationship IfcRelationship IfcRelDefines->IfcRelationship IfcRelationship_children 5 more... IfcRelationship_children->IfcRelationship IfcRoot IfcRoot IfcRelationship->IfcRoot IfcObjectDefinition IfcObjectDefinition IfcObjectDefinition->IfcRoot IfcPropertyDefinition IfcPropertyDefinition IfcPropertyDefinition->IfcRoot Definitions applying to General Usage Identity

IfcRoot assigns the globally unique ID. In addition it may provide for a name and a description about the concept. Revision Control

Ownership, history, and merge state is captured using IfcOwnerHistory. Formal representations

ENTITY IfcRelDefinesByObject
 SUBTYPE OF (IfcRelDefines);
	RelatedObjects : SET [1:?] OF IfcObject;
	RelatingObject : IfcObject;