A datatype can have values TRUE, FALSE, UNKNOWN or UNSET. 
Namespace: Autodesk.Revit.DB.IFC
Assembly: RevitAPIIFC (in RevitAPIIFC.dll) Version: 24.0.0.0 (24.0.0.0)
Since:  2013 
Syntax
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Namespace: Autodesk.Revit.DB.IFC
Assembly: RevitAPIIFC (in RevitAPIIFC.dll) Version: 24.0.0.0 (24.0.0.0)
Since:  2013 
| C# | 
|---|
|  | 
| Visual Basic | 
|---|
|  | 
| Visual C++ | 
|---|
|  |