This is where the commands are kept. The three packages are

sm - the raw model commands. look there for commands changing the modelelements
di - the diagram commands. usefull for adding a representation of an existing modelelement to another diagram
dism - the combined commands. They are the most useful and most needed ones: for example, if you want to create
an association, then the dism-command CommandCreateAssociation will use one sm-command for creation, and one for
adding the representation to the current diagram