With V8, Bentley introduced MicroStation users to the concept of models. Whereas a V7 design file used to be one single design space, a V8 design file is a container of models, each of which behaves much like a separate design file. You can create an unlimited number of models in a DGN file.

There are two types of models: design or sheet. Design models can be either 2D or 3D. A design model can also be used as a reference or placed as a cell. Sheet models, which are flat and used for drawing composition, are ordinarily 2D (see description of "drawing composition" below). Sheet models let you attach references to create a set of working drawings for the design. By default, the view windows of design models have black backgrounds and those of sheet models have white backgrounds.

MicroStation users familiar with AutoCAD will notice that the model concept is not new to CAD. A design model is similar to the "DWG model space" and a sheet model is similar to the "DWG paper space".

Drawing Composition
As the name suggests, design models are meant to serve as design environments, where designers can draw components or sections of an overall design and then use sheet models to bring together parts and compose finished, annotated drawings. This is a concept known as "Drawing Composition". In other words, you can reference in models from the same file into another model in the same file (or another design file if you want). For example, you can design the drawers for a desk in one design model, the table top in another and bring them all together as a complete desk in the sheet model.

Models dialog box
MicroStation V8 offers a simple dialog box to manage models. The Models dialog box can be accessed through File | Models or by clicking on the Models icon.

The Models dialog box is explained in the graphic below:

The Models dialog box (File | Models) is used to create and manage models in an open DGN file.

Useful model key-ins
If you are like most of us at Axiom (read: a geek), then the following key-ins will help you move faster. You can either memorize them or assign them to a function key. Enjoy!

• Create a new design model: MODEL CREATE DESIGN
• Create a new sheet model: MODEL CREATE SHEET
• Import all models from another design file: MODEL IMPORT ALL

These key-in commands will prompt for any additional information they need.

Drag and drop models
You can also drag and drop DGN or DWG files from Windows Explorer into the Models dialog box to import the models from the selected files. Similarly you can use drag and drop to drag models from the Models dialog in another open session of MicroStation to the Models list box and drop them in to import the models. Neat!

Models! Models! Models!
Models have changed the way MicroStation designers work, by providing multiple design environments within one file. This translates to fewer numbers of files per project and easier management of design information. Yet another clever way Bentley has given us to more efficiently communicate design intent.