Add-ons are components with which a SiSy output can be expanded to include certain functions, diagrams or other properties. SiSy is essentially a general modeling tool, which is adapted for the respective modeling task via a metamodel. The different editions of SiSy are ultimately a coordinated set of add-ons. As a rule, each SiSy edition can be supplemented with additional add-ons. It should be noted, however, that there are cross-relationships between some add-ons.