Ideally, building information created by a firm using any CAD software should be equally accessible to another firm using different CAD software. At the file level, this degree of standardization requires either sophisticated file import and export routines in each program or the ability to read from and write to a common format. Document-level standardization involves grouping drawing elements into sets, called layers or levels in most CAD programs. To share their work, early CAD users organized CAD information according to similar layers. Walls and doors, for example, are grouped separately.
Most design firms develop an in-house layering standard, but few agree on the same one.
Facility owners with many buildings can manage their operations more effectively if CAD documents for all their buildings follow the same layering standard. Some large client organizations impose their own layering systems on their consulting architects. For the design firm, the resulting multiplicity of standards followed for different projects is almost as bad as having no standards at all. The absence of a universal layering standard prevents client A from working with CAD files prepared by architect B, even when both use the same program. Similar incompatibilities arise when CAD programs translate internal representations or models of building designs into traditional plan, section, elevation, and detail drawings.