A free model (FEM) provides a context-free environment for modeling any kind of objects or systems. It is generally associated with a set of extensions, which allow you to define your own concepts and graphical symbols.
To create a new, empty FEM - Select , and choose Free Model.
For information about extending objects from their property sheets, see Extending Objects. For detailed information about all the extension mechanisms available in PowerDesigner, see Customizing and Extending PowerDesigner > Extension Files.