Before proceeding with a discussion of ModelMaker's UML support and other features, it is vital that you understand conceptually how ModelMaker manages your code model. Unlike Delphi and other editors, ModelMaker does not continually parse a source code file to visually represent the contents. Consider Delphi: Any IDE convenience you use to alter your code will directly change the contents of the source code file (which you can then save in order to persist the changes). In contrast, ModelMaker maintains an internal model representing your classes, code, documentation, and so on, from which your source code files are generated. When you edit your model through the various editors in ModelMaker, the changes are applied to the internal model—not the external source code files; at least, not until you tell ModelMaker to regenerate the external files. Understanding this distinction should save you some frustration.
Another concept to understand is that ModelMaker is capable of representing a single internal code model with multiple views in its user interface. The model can be viewed and edited, for example, as a class hierarchy, or as a list of units with contained classes. Class members can be sorted, filtered, grouped, and edited in a variety of ways. Any number of views can be seen in the various plug-ins available for ModelMaker. But most important for this discussion, the UML diagram editor itself is another view into the model. When you visualize elements of the model (such as classes and units) in your diagrams, you are creating visual representations of the code model elements; if you delete a symbol from a diagram, you are not necessarily deleting the element from the model—you are simply removing the representation from your diagram.
One last consideration about diagramming in ModelMaker: Although ModelMaker offers several wizards and automation features in the area of visualization, the product will not read your code and magically produce attractive UML diagrams with no effort on your part. Upon importing your source code and adding your classes to diagrams, you will need to arrange the symbols in order to create usable UML diagrams.