This means that you can create a custom IFC Property and the values and fields of that IFC Property will come from a Classification, such as Onmiclass, Uniformat, etc.
However, since the Classification Manager was introduced in ARCHICAD 21, it is a better solution to use the Classification Manager to create such Classifications, since any element can have any number of Classifications, according to various Classification Systems.
As a general direction, with the introduction of the Property Manager and the Classification Manager, GRAPHISOFT made it unnecessary to create custom IFC Properties since you can do them in the Property Manager and the Classification Manager.
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