IfcRelFillsElement is an objectified relationship between an opening element and an element that fills (or partially fills) the opening element. It is an one-to-one relationship.
NOTE View definitions or implementer agreements may restrict an opening to be filled by one filling element only.
As shown in Figure 1, the insertion of a door into a wall is represented by two separate relationships. First the door opening is created within the wall by IfcWall(StandardCase) <-- IfcRelVoidsElement --> IfcOpeningElement, then the door is inserted within the opening by IfcOpeningElement <-- IfcRelFillsElement --> IfcDoor.

HISTORY New entity in IFC1.0
| # | Attribute | Type | Description |
|---|---|---|---|
| IfcRoot | |||
| 1 | GlobalId | IfcGloballyUniqueId | Assignment of a globally unique identifier within the entire software world. |
| 2 | OwnerHistory | OPTIONAL IfcOwnerHistory | Assignment 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. |
| 3 | Name | 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. |
| 4 | Description | OPTIONAL IfcText | Optional description, provided for exchanging informative comments. |
| IfcRelationship | |||
| IfcRelConnects | |||
| IfcRelFillsElement | |||
| 5 | RelatingOpeningElement | IfcOpeningElement | Opening Element being filled by virtue of this relationship. |
| 6 | RelatedBuildingElement | IfcElement | Reference to ~~building~~ element that occupies fully or partially the associated opening. > IFC2x CHANGE The data type has been changed from IfcBuildingElement to IfcElement with upward compatibility for file based exchange. |
IfcRoot assigns the globally unique ID. In addition it may provide for a name and a description about the concept.
Ownership, history, and merge state is captured using IfcOwnerHistory.
ENTITY IfcRelFillsElement SUBTYPE OF (IfcRelConnects); RelatingOpeningElement : IfcOpeningElement; RelatedBuildingElement : IfcElement; END_ENTITY;