Freja is launched from within the Mjølner tool one of the following ways:
In the source browser select the UML toolbar button . If the code editor is empty a new diagram with corresponding code may be created. If the code editor contains an Attributes fragment form or a Descriptor fragment form with declarations, the fragment form will be shown in Freja as a reverse engineered diagram of the code in the fragment form. Note that relations, like specializations and associations, will only be reverse engineered if the fragment has been checked (e.g. using the Check toolbar button). Also note that if a diagram already exists for the selected fragment this will be opened and possibly be updated.
In the source browser open a BETA fragment form. Right-click anywhere in the code editor and select Show UML Class Diagram from the popup menu. This will have the same effects as mentioned above.
Mjolner Integrated Development Tool - Reference Manual