Bind/export linked files - while having consistency in generated element ID's

[Anonymous]

I try to export a Revit model with linked files to IFC file format, while having consistency in the element ID’s in the IFC file (GUID). So after updating my Revit model and subsequently bind linked files + exporting to IFC again, I want to have the same element ID's as in the previous bind/exported IFC file (or the same GUID's).

However, in the process of binding the linked files there is no consistency in the generated element ID’s, compared to previous versions of the same model. I'm looking for a solution for this. 

The BIM model is residential building with a lot of repetition, hence, the model is set up with linked files and duplicates of the linked files (and we aim to keep it like that):

• We have a model from a typical apartment of the building (‘unit model’), and that model is linked in a level model of the building. The linked unit model is copied to create a complete level of the building. This model we call a ‘level model’.
• This level model is linked in the main model of the building (called a ‘block model’) and copied over the other levels of the building to create the full block model of the building. 

 Please see example below.

To export the main model (block model) to one single IFC, I tried to bind the linked files (incl the duplicates of the linked files) in the main model, and subsequently export the full model to a (single) IFC file. In the process of binding the linked files, element ID’s are generated for the parts that were linked before. However, the generated element ID’s are not consistent if we repeat this binding process. So every time we bind the same linked files, different element ID’s are assigned to the BIM objects. This is where I need consistency element ID’s, because after updating my Revit model and exporting again to IFC, I want to have the same element ID's as in the previous IFC file (or GUID's).

I already explored several solution by avoiding binding of the linked files, but all without effect:

• Using Groups instead of linked files, to avoid binding of linked files
• Leads to larger BIM models which are hard to handle in Revit
• Use the Revit option to ‘Export linked files as separated IFC’s’ to avoid binding of linked files
• Generates from the duplicated linked files in the main model separated IFC files but the element ID’s inside the IFC files are the same (so the BIM elements in the IFC file of level 2 have same ID as BIM elements in IFC file of level 3).

 I’m wondering if there is any approach for:

• have consistency in the generated element ID’s while binding linked files into a Revit model OR;
• exporting Revit files with linked files to one single IFC, while having consistency in the generated element ID’s

[L.Maas]

I think you are running into issues here. Each Revit file will have unique element ID's. When you delete an element from the file then that element id will not be used again. However element ID's are (as you experienced) not unique between different Revit files. So when you bind Revit links you are pushing everything in a single file. Internally Revit will sort out the element id's. If the linked file has an element with a same element id as in the host file, Revit will assign a new element id. You do not have control over this. So there is no sure way to have consistency in the newly generated element id's.

So in your case I would forget about element id's. They are not suitable to uniquely identify elements between different files

Is there a specific reason you want to use element id's?

You might look into the option of during the export to IFC to store the IFC GUID in a revit parameter of the corresponding element.

[Anonymous]

Thanks for your reply Louis (bedankt!).

No specific reason to use element ID's, I only need a unique ID for each objects to follow. Just thought element ID's would be the easiest solution, but then the issue in case of binding linked files popped up.

I'm also considering indeed storing the IFC GUID in a parameter. That could be a direction. We could use the option to create a separated IFC file of each linked file and make use of the option to store the IFC GUID in an element parameter. Then, for each level where we copied the linked file, we get a separated IFC file. The elements in each IFC file would have the same GUID though. I could make them 'unique ID's' by for example using Dynamo to add a sub-ID, for example make unique ID = "GUID + level number" (since we copy the linked files over the different levels).

However it seems like when I export the linked files to separated IFC files, it's not storing the right level in the IFC file parameters. If the we placed the linked file on level 1, and copied it to level 2 - 5, in the exported IFC all 5 levels still have level 1 in their parameter..

any tips for this direction?