Since it is often very hard to select a single link with the mouse in a dense web of links, in this simulator all selections of links are done with the reference to units. That is, links are selected via their source and target units. To select a link or a number of links, first a unit or a group of units must be selected in the usual way with the left mouse button (indicated by crosses through the units). Then the mouse pointer is moved to another unit. All links between the selected set of units and the unit under the mouse pointer during the last key stroke of the link command are then selected.
Example (deleting a group of links):
All links from one unit to several other units are deleted as follows: First select all target units, then point to the source unit with the mouse. Now the command Links Delete from Source unit deletes all the specified links.
As can be seen from the examples, for many operations three types of information are relevant: first a group of selected units, second the position of the mouse and the unit associated with this position and third some attributes of this unit which are displayed in the info panel. Therefore it is good practise to keep the info panel visible all the time.
In section 
a longer example dialogue to build
the well known XOR network (see also figure ) is
given which shows the main interaction principles.