Sets the value of PredefinedType attribute. This attribute represents predefined generic type for a slab that is specified in an enumeration. There can be a property set specified specifically for the predefined types.

• The PredefinedType is only used if no IfcSlabType is assigned, providing its own IfcSlabType.PredefinedType
• IFC2x CHANGE The attribute has been changed into an OPTIONAL attribute