Consistent ElementIDs when generating a model using an IFC file

[josepht21]

Hey everyone!

I have a question related to IFC and Revit Element IDs. I recently imported an IFC file that I generated in another software and linked the result to an empty Revit file where I added many hosted elements (like HVAC systems and such). My issue now is that because all those hosted elements depend on the Revit ElementID to connect to the correct host, if I reimport a modified IFC model (after making changes in the other software) the Revit Element IDs won't necessarily be consistent to the original import and the hosted elements will lose their host.

Any idea of how to make sure the IDs of Revit Elements remain consistent? Meaning importing similar IFC files which share IFC GUIDs get the same Revit ElementIDs for the same IFC objects.  

@jeremy_tammik 

[barthbradley]

Huh? Can you elaborate? What do you mean hosted elements depend on the Revit ElementID to connect to the correct host?   

[josepht21]

Each Revit Element (Wall, Floor, Column, etc.) has a unique Revit ElementID. When you add a hosted element, for example a Window into a Wall, Revit knows they are connected via their ElementIDs. Therefore the host element of the Window is the Wall and the way they connect each other is by stating that the Host of the Window equals to the ElementID of the Wall.

[barthbradley]

Huh?  Are you serious or just messing with me?  

[noamgatCXBC7]

I think that the author is referring to the fact that hosted elements have an internal ID of the element that is hosting them. The building coder blog has a few articles on retrieving these ids ( https://thebuildingcoder.typepad.com/blog/2009/06/host-reference.html , https://thebuildingcoder.typepad.com/blog/2010/08/transaction-migration-errors.html ).

What I think that the author is experiencing, is that if the host element comes from a linked document which was imported from IFC, the link between the host and the hosted will break if the IFC is reimported (because the internal IDs are not the same), and he is wondering if there is a way to prevent this delinking.