In many cases, particularly on large projects, it may be that a design model consists of the active model, plus one or more references to other models. These references may be to other models contained in the open DGN file, or they may be models contained in other DGN files.
When other models are included as references to the active model, they still retain the link to the original model. This means that any changes to the original model will be reflected in the references. Using references gives you the option of having several designers work on a project simultaneously. For example, a civil designer could be working on the earthworks model, an architect on the building model, and a mechanical designer on the plant model. Each could have the other models referenced to their own model to keep abreast of any design changes in the other disciplines.
Referencing Design Models in Sheet Models
Creation of hard-copy prints of your designs, in the form of drawings, requires initial setting up of sheet models. A sheet model typically consists of a collection of design model references that are scaled and positioned as necessary to create a drawing, usually inside a drawing border, which can be printed.
In the sheet model, you then add dimensions and other notes as required. You can use the reference tools to manipulate the references as needed to create the drawing. Typically, this may include folding, copying, scaling, clipping, rotating, masking, and/or mirroring the references. When working with 3D references, you can use visible edges settings to display the reference correctly for the drawing.
Sheet models can be thought of as virtual sheets of paper, which are printed to produce hard-copy documents. Design geometry that appears in a sheet model is attached as references, either from models in the same DGN file, or from models in other DGN files, or a combination of both.