AEC Tech News #94 (Mar. 27, 2003)

26 Mar, 2003 By: Lachmi Khemlani

In AEC Tech News #90, I introduced the concept of "Building Information Modeling (BIM)," the latest buzzword in the AEC industry that is ostensibly set to replace the term "CAD". We saw how Autodesk is positioning Revit, a parametric modeling application with a central building model, which it acquired last year as its BIM solution of the future. I also pointed out how the concept behind BIM is not new: neither in academia, where it has been the subject of much research and prototype development, nor in the industry, where tools such as ArchiCAD incorporated the single building model concept right from the start.

The BIM Race

With the industry's largest vendor, Autodesk, pushing BIM in a big way, a new wave of competition has been unleashed. By urging its customers to grow out of 2D CAD, think 3D BIM, and switch to Revit, Autodesk seems to have also inadvertently leveled the playing field for other vendors as well. Both Bentley and Graphisoft have jumped onto the BIM bandwagon, not to be outdone. They are touting the superiority of their respective BIM solutions, hoping to not only retain their current user base but also attract current AutoCAD and Autodesk Architectural Desktop (ADT) users who will soon reevaluate their 3D BIM options. To this end, we have seen white papers on BIM, along with promotional events such as road shows and world tours, from each of these vendors. So, if you are an AEC professional, you are not going to get very far these days without hearing about BIM!

Having discussed Autodesk's take on BIM in Issue #90, centered on its Revit application, this issue presents a brief overview of Bentley's approach to BIM, which is substantially different from Autodesk's.

Bentley's View of BIM

Bentley's key strategy for BIM, in direct contrast to Autodesk's switch to a new application, is "not starting over." In fact, Bentley sees starting over as not only unnecessary but also dangerous and wrong, given the investment by users in current tools, data, and workflows. In this regard, Bentley's position comes directly from its client and project profile; its software is used by many of the top design firms for large-scale projects that span years rather than months, such as airports, stadiums, offices, campuses, stores, and manufacturing plants. Therefore, switching to a new software is not a practical option. This makes Bentley advocate an "evolutionary" rather than "revolutionary" path to BIM, determined by the users' own pace.

Even if a switch were practical, Bentley believes its users do not need to do so as it already has a strong BIM solution, comprising its core MicroStation platform and all the building design and collaboration applications built around it. In contrast to its competitors, Bentley is adopting a "federated database" approach to BIM, where all the data related to the building is not centralized (as in Revit's or ArchiCAD's single building model) but is, instead, distributed across multiple applications and data stores in a coordinated fashion. Bentley finds the centralized data model approach inherently unworkable; the company argues that any application with such a model is not scalable, cannot support large building projects, and will collapse under its own weight.

In short, there is more to BIM than just a single tool or model, and Bentley sees itself as the only vendor to have an integrated, multi-disciplinary BIM solution built on a unifying platform, rather than only individual tools. BIM is a superset of CAD, and Bentley wants to provide its users with a "ramp" as a transition path from CAD to BIM, without abandoning current capabilities. The strategy of the company would be to stay focused on MicroStation as the single, comprehensive platform, extend and improve it with compatible applications, and augment it as needed with server-based collaboration tools.


In AEC #90, I discussed the difference between a geometric data model and a building data model, and how the latter lies at the heart of any application that purports to support building information modeling. Autodesk's move to Revit as its future BIM solution is prompted by the fact that its other building design solution, Autodesk Architectural Desktop (ADT), is built on top of AutoCAD's geometric data model, which limits its BIM capabilities. Likewise, Bentley's MicroStation TriForma is built on top of a geometric data model. However, unlike ADT, it uses a federated database to store and manage information outside of geometric file formats such as DGN and DWG. How does this affect its BIM capabilities? And how does Bentley Architecture (formerly know as "Architecture for TriForma") compare with applications such as Revit and ArchiCAD that were developed with a building data model right from the start? I will explore these aspects in a future issue of the AEC Tech newsletter.

With regard to BIM, it is going to be difficult, at least in the near future, to even pinpoint the characteristics of a good BIM solution, let alone evaluate which approach is the best or which existing solutions are the most effective ones. The situation is analogous to the early days of CAD, where it was not very clear as to what a CAD system should do. Computer aided drafting? Computer aided design? Or both? Eventually, CAD systems evolved, their capabilities became clear, standards were set, and it was possible to do a comparative analysis of CAD systems based on their specific features. We will eventually get to the point where we can specifically determine what a BIM solution is expected to do and what features it needs to have. Currently, it is all very loose and fuzzy, with some vendors such as Autodesk calling for radical changes, while others such as Bentley emphasizing the opposite--that there is no need to start over.

One thing is clear though--we are at the threshold of something new in the building software industry. It will be interesting to see how the BIM saga unfolds.

Relevant Links

Bentley's white paper on BIM: