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.