5D, 6D and even more

5D, 6D and even more 

3D goes without saying: the things architects design are made in 3D, so it's an obvious necessity. 4D is interesting, especially if the addition of the temporal dimension is not just an arbitrary time stamp but a product of interdependence between objects and actions: it's logical that a wall should be painted after it has been plastered but it does happen that even these basic things are poorly planned.

What about 5D, 6D and more - which are these dimensions, where do they come from? In most cases, 5D in BIM refers to cost. This feels like a letdown. Technically, one could find support for adding a new information type to a representation and calling it a dimension. However, looking at it from the viewpoint of semantic information, cost is derivative information: something that can be calculated on the basis of primary information, i.e. quantities and qualities in the model, contextual information that determines difficulty in execution, the need for special equipment etc. Any additional information like prices for materials and labour derive from external, linked sources rather than the model itself.

A basic rule in any information system is to never include derivative information. For example, the birth date of a person is explicitly found in a database but the age of this person is just calculated on the basis of their birth date. Similarly, in BIM the floor area of a space is not a dimension we add to the object but a calculation of two properties corresponding to two dimensions. Consequently, I'm inclined to dismiss 5D, 6D etc. in BIM as redundant and counterproductive - and I don't care to hear counterarguments about metaphors and the like: such constructs should elucidate, not obfuscate.

3D

3D

When most people talk about 3D, it's about depth perception, about combining two pictures of a scene (as we do with our two eyes) to actually see rather than infer the distance and relative position of objects. In architecture, when we talk about 3D, it's about the height of objects, the Z axis in our representations. This is arguably typical of architecture: we don't look at the world, we look at our own tools and conventions. Perhaps the saddest thing is that we don't appear to celebrate the ingenuity of these tools: 2D representations aren't boring, stupid means to be replaced by 3D representations as soon as possible; at least some of them are great ways of describing aspects of the real world, making them accessible and manageable.

No, I'm wrong: the saddest thing was that many years ago, when I was pushing for 3D and making people work towards it by putting floor plans on top of each other and cross sections at the right places, discrepancies of even 50 cm between floors were not uncommon. Of course, at the same time, when we put floor plans of adjacent buildings next to each other we discovered gaps of up to fifteen degrees. That's the saddest: not being able to use one's tools properly - and this won't improve with 3D.