The usual workflow collaborating with third parts or consultants is one of the openBIM keys. If our software is capable of transferring these new parameters from the 3rd part IFC files into the AC native fields (properties) it would be cool.
In any case, you need to know where you want to use this external IFC file new properties, because maybe you can just use the IFC labeling for layouting.
And if you want to transfer a new IFC model, maybe you'll need to federate these several IFC files within another IFC software, like Tekla BIMSight or something like that.
David Delgado Vendrell
http://www.daviddelgado.cat
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Surfing with Archicad since 2013