BIM and the geometry trap

I've been working with BIM for more than a decade now. I started with Revit, shifted to an IFC-based workflow since 2019, and before that, spent years in 2D CAD. While 3D visualization existed alongside engineering workflows, it was mostly limited to arch-viz.

Over the years, my understanding and definition of BIM has evolved too. Simply put, BIM stands stands for Building Information Model, ie, it's a model of the building with information.

So what constitutes this "information"? What Level of Information (LOIN) or what Level of Detail (LOD) is required in the model to be called as a BIM? We've all come across various SaaS/Software solutions claiming them to be BIM? Is BIM exclusive to giants like Revit, or can smaller tools qualify if they hold information/data? Does BIM require 3D geometry? What if there is no geometry at all - is it still a BIM?

In the IFC Schema (IFC is the ISO standard for BIM - ISO 16739), geometry is just like a property that is assigned to the element. There could be various geometry that can be assigned to the element - a BREP (Boundary Representation), a tessellated Mesh, a Constructive Solid Geometry, point cloud, or even a 2D CAD. What if there are no geometry assigned to an element? By definition, this is still a valid BIM

So, what makes a model truly BIM? I would define this as a model that has information, and also intelligence. It should be queryable.

Is 2D CAD a BIM? CAD also has information, but lacks inherent intelligence? However, if we inject intelligence into 2D CAD, does it not become a BIM? If you strip away the geometry debate and focus on what actually matters - structured, queryable, semantically rich information about a building - then a 2D drawing with intelligence layered on top is absolutely a Building Information Model.

And, what does a BIM look like without geometry? At its core, it's entities, their properties, and the relationships between them. But, that's a conversation for another time.