BlenderBIM, IFC Construction Type / IfcBuiltElementType confusion

Hi! Is "IFC Construction Type" specific to Blender BIM? I can not find that term used in the IFC documentation.
I see that for instance walls exported from Revit gets a IFC Construction Type set to a wall type. Isn't that an IfcBuildingElementType or an IfcBuiltElementType?

Comments

  • Yes, the naming is BB specific, but it refers to the same thing as IfcBuildingElementType/IfcBuiltElementType. I think it was just renamed to "Construction Type" to make it more user-friendly.

    EinarAceCadGiru
  • It represents the IfcElement <-- IfcRelDefinesByType --(RelatingType) --> IfcElementType relationship. In non-technical jargon, I believe it is best represented by calling this the "Construction Type". (e.g. you have a wall types drawing, or a beam types schedule, or an equipment types schedule, etc. It's a bit of an umbrella term for the ways types are used in construction.

    Imagine you have a wall, if you ask "what type of wall is it?" The answer is something typically like "it's a 200mm thick core filled block wall" ... i.e. a wall type.

    If you have a beam, you might ask "what type of beam is it"? The answer is typically something like "a 200UB" ... i.e. a beam type. Notice whereas the wall type describes the wall layer build up, structural beam types typically instead describe cross sections.

    If you have a pump, you might ask " what type of pump is it?" The answer is typically something like "A model number "QPX" from manufacturer "Acme Pumps" dual flow reticulating ultra pump" (obviously, I am not a hydraulics engineer and I made it all up), ... i.e. a pump type. Notice this time, the equipment correlates to a literal product you can buy / procure from a manufacturer, which has a supplier, warranty provider, and will have a model number you can order for replacements and a correlating section in an operations and maintenance manual.

    If you have a set of kitchen joinery in an apartment you might also ask "what type is it"? This time the answer might be simply something like "Type 2B", which represents the fact that there are a few standard joinery configurations in the apartment, and one of them happens to be documented as Type 2B in the architectural drawings. As you can see, this "Furniture Type" yet again has a slightly different definition to the way types are used for walls, beams, and pumps.

    Despite these differences, they all answer the same semantic question of "What type of X is it"? They also share the common concept that occurrences of that type share properties that are common. E.g. the fire rating of a wall type is the same across all wall occurrences.

    Maybe it should be renamed to just "IFC Type"? I added the word "Construction" because I felt sometimes it helped remind people to think of it in terms of how types are split for analysis / procurement / installation in construction (and later, commissioning which would then align with building maintenance), which is the inherent purpose.

  • Thanks for the detailed response! I love to use tools like IfcOpenShell and BlenderBIM to explore the IFC schema raw and free. In the beginning I used software like Solibri which creates their own names for most of the entities and attributes. That's not helpful for anyone trying to understand IFC better.

    If I understand it correctly, the ifc docs chapter 4.6.1 explains this concept as "Object Typing" and uses the term "object type entity".

    Maybe "IFC Object Type" could be an alternative. Of course that is easy to confuse with "ObjectType" which is an attribute that allows for custom values when there is no "Object Predefined Type". Just "IFC Type" is probably fine.

    Arv
  • Agreed, would you like to help submit a PR to make this change?

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