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AEC from the Ground Up-CAD Data Standards for AEC

August 1, 2006 By: AIA ,H. Edward Goldberg

Collaboration in AEC depends on mandated or de facto standards.


We are now in the third decade of digital AEC design and documentation, enough time for the industry to create or adopt both actual and de facto standards. Among these are standards for raster or bit-mapped images, document compression schemes such as Adobe PDF and Autodesk DWF and vector information used in construction documents.

In the digital world, the appropriateness of any particular standard is mostly a function of what you want to do with it. As an example, ASCII is perfectly appropriate for representing the English alphabet, but is useless for representing Kanji, Katakana, Cyrillic and other writing systems. A standard called Unicode has been developed to deal with them.

Figure 1. Adobe Acrobat 3D software lets engineering and technical professionals publish and share 3D design information from major CAD applications.
Figure 1. Adobe Acrobat 3D software lets engineering and technical professionals publish and share 3D design information from major CAD applications.

Standards such as JPEG, TIFF and IFC (Industry Foundation Classes) are standards that were created by committees and adopted by industry organizations. A de facto standard such as DWG or PDF becomes a standard not through the blessing of a standards organization but by broad grassroots adoption and recognition throughout an industry.

Some standards are unique to AEC: layering standards such as NCS (National CAD Standard) and steel detailing and integration standards such as CIS/2. We even have a de facto green building standard called gbXML. gbXML became the draft schema for the International Alliance for Interoperability's Building Performance and Analysis working group.

In this article
In this article

This article is not a defense of any standard, but rather an overview of the common data formats in the AEC world.

Autodesk and DWG

DWG is the native format for Autodesk's AutoCAD-based products, which, according to Autodesk, have more than seven million users worldwide. Autodesk has never documented the DWG format, but it does provide a software development kit, RealDWG, that third-party developers can use to add read/write support for DWG to their applications. It's used internally by Autodesk to provide DWG support in non-AutoCAD products such as VIZ, Revit and Inventor.

Open Design Alliance and DWG

The Open Design Alliance develops software libraries to enable import and export of DWG files. These libraries are used by many of Autodesk's customers and competitors. Formerly known as the OpenDWG Alliance, the Open Design Alliance was founded as a nonprofit membership-based consortium by software developers, including Visio, ESRI, Bentley and SolidWorks.

Figure 2. Autodesk Design Review, formerly known as Autodesk DWF Composer, has many new features and functions added after requests from building industry customers.
Figure 2. Autodesk Design Review, formerly known as Autodesk DWF Composer, has many new features and functions added after requests from building industry customers.

Open Design Alliance president Evan Yares is very vocal about the DWG format:

The most important container format in the AEC CAD industry is DWG. It may seem odd that I'd refer to it as a container format, but DWG files can contain text, various forms of images, 2D linework, 3D models and more. While we tend to talk about DWG as a single monolithic format, the reality is that there are at least 30 variants of DWG out there. This situation presents an almost intractable problem when DWG is used as the primary conduit of design data in an extended project lifecycle. Downstream consumers of design data can never be sure if they'll actually be able to use the DWG files they're getting. 

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