Here is from a patent application by Autodesk:
“A method, system, apparatus, and computer program product provide the ability to augment an as-built model. A CAD drawing of a project as well as a digital representation of a physical implementation of the project are obtained.
A relationship that maps the digital representation to the CAD drawing is defined/established. A component of the digital representation is identified based on the relationship (e.g., and a database/catalog). Information about the identified component is transmitted to and displayed on a computer (e.g., a mobile device).”
For more details on the patent see US 2012/0116728 A1
Via WorldCAD Access