The Dimensions of BIM!?
Starting from the considerations discussed in the previous article, “BIM… what?”, which you can find here, we can state that the entire BIM process is based on the use of the Information Model.
I would like to make one point clear from the outset: an Information Model is not simply a generic 3D model of a built asset from which we may extract two-dimensional (2D) information, as those who are less familiar with this technology unfortunately often tend to believe. It is something considerably more complex.
ISO 19650 defines an Information Model as a “set of structured and unstructured information containers” [1], where an information container is understood as a “named persistent set of information [2] retrievable from within a file, system or application storage hierarchy” [3]. Moreover, “structured information containers include geometrical models, schedules and databases, while unstructured information containers include documentation, video clips and sound recordings” [4].
Below is a hierarchical representation of an Information Model based on the principles described in ISO 19650.
Another important clarification: the definition of information container should not lead to another misconception. An Information Model is not simply a 3D model to which other types of information, such as Excel spreadsheets and similar files, are linked and/or imported, as is often mistakenly assumed.
Strictly speaking, the Information Model should not even be conceived as a single 3D model, because three-dimensional space accounts only for its first three dimensions. In reality, it should be regarded as a higher-dimensional entity, borrowing the concept of extra dimensions from physics.
Starting from three-dimensional space, the Information Model first incorporates the well-known fourth dimension, time (4D), and then three additional dimensions: cost (5D), management (6D) and sustainability (7D) [4], for a total of seven dimensions.
How can we spatially imagine an object that extends beyond the three or four dimensions we experience in everyday life? Quite frankly, we cannot. Conceptually, it is almost impossible to visualise. And yet, this is precisely what an Information Model is.
Below is a conventional representation of the dimensions of an Information Model.
Understanding the Information Model is perhaps easier if we draw an analogy with a physical model, a mathematical model, an economic model, and so on. In other words, it can be understood as a tool created to make it easier to solve problems belonging to the real world, a world that is certainly more complex than one consisting merely of length, width, thickness and time.
Like the other types of models mentioned above, the Information Model is created by starting from the reality of the AEC world, adopting the principles that govern it, space, time, costs, sustainability and management, and transferring them into a virtual environment through a series of simplifications that make the model itself easier to understand, manage and control.
The ultimate result is a solution intended to materialise in the real world, thereby supporting and facilitating the design, construction and management of a built asset.
A model that lacks any one of its dimensions is an incomplete model. A 3D-only model is not BIM.
The Information Model is therefore an extremely powerful and complex tool whose generation clearly involves the use of several different software applications.
This brings us to another concept that should be firmly established, while dispelling yet another widespread myth about BIM: there is currently no single software application capable of creating and modelling an entire Information Model on its own, despite what software companies occasionally, and somewhat opportunistically, try to suggest.
At present, an Information Model can only be developed through the combined use of various BIM-workflow software applications known as BIM Authoring tools, each of which is designed to model one or more dimensions of the Information Model.
It is also important to clarify the meaning of the term modelling in a BIM context. Here, modelling does not refer exclusively to the creation of 3D geometry, as it typically does in a CAD environment. Instead, it encompasses all the operations performed by software to create and/or modify one or more of the seven dimensions of the Information Model.
When it comes to Information Model authoring, the tools best known among industry professionals are probably the so-called 3D BIM Authoring tools, including Revit, Allplan, ArchiCAD, MicroStation, Tekla, and others.
However, the BIM ecosystem also includes a considerable number of other software applications dedicated to the remaining dimensions of the Information Model. To name just a few examples: Synchro PRO and Navisworks for 4D; STRVisionCPM and PriMus for 5D; STRVisionAM and dRofus for 6D; and EdilClima and Termolog for 7D.
Anyone with even a basic knowledge of the applications mentioned above will immediately notice, however, that most of the software associated with the 4D, 5D, 6D and 7D dimensions of the Information Model already existed, to a large extent, before the advent of BIM.
The BIM revolution therefore led their developers to integrate Information Models into their software in various ways.
By contrast, 3D BIM Authoring tools were specifically conceived and developed for the creation of Information Models. It was largely thanks to the emergence of these applications that BIM was finally able to move from theory, whose earliest conceptualization is generally traced back to 1974, when Professor Charles Eastman published An Outline of the Building Description System – BDS, to effective practical implementation.
So, what is the difference between a 3D BIM Authoring tool and 3D CAD software?
I would say: all the difference in the world.
It is precisely within this distinction that both the BIM methodology and the Information Model as a tool reveal their true essence.
But we will explore this topic in detail in the next article.
Cover background is designed by macrovector / Freepik
[1] ISO 19650-1:2019, p. 4, point 3.3.8
[2] ISO 19650-1:2019, p. 3, point 3.3.1
[3] ISO 19650-1:2019, p. 4, point 3.3.12
[4] ISO 19650-1:2019, p. 5, point 3.3.12, Note 1
[5] UNI 11337-1:2017, p. 3, from point 3.1.4 to point 3.1.9