IFC Attributes

IFC Attributes are the main identifiers of IFC Entities. The names of IFC Attributes are fixed, having been defined by buildingSMART as part of the IFC standard code.
In the case of ARCHICAD, most of these IFC Attribute names are derived from the project. For example, the IFC Attributes of an IfcWall building element:
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GlobalId: the Globally Unique Identifier of the IfcWall in the IFC model (not editable).
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OwnerHistory: the assignment of the information about the current ownership of the IfcWall.
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Name: its factory-default derived value is IfcWall’s ARCHICAD ID (Wall Settings dialog box > Categories and Properties panel).
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Description: an optional textual description.
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ObjectType: an optional text to define a subtype of an element or add type information to it.
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Tag: its factory-default derived value is the IfcWall’s ARCHICAD “Unique ID” (not equal to IFC GlobalId).
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In order to provide fast access, OwnerHistory is directly attached to all independent objects, relationships and properties. Its components and values are derived from project data and hidden in the ARCHICAD user interface. It includes for example the owning actor (OwningUser) of which multiple values are derived from ARCHICAD’s Project Info (File > Info).
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“Factory-default” means that as long as no custom data is entered, and as long as the value has not been mapped using a rule (see IFC Scheme Setup), the program provides this value for the Attribute.