ISY-99i/ISY-26 INSTEON:Program References
Program references allow you to isolate a set of actions to be run, or a set of conditions to one location, and reuse them in many different programs. For example, a program containing the schedule for office hours could be created and used by many other programs. If the office hours change, only the office hours program itself has to change, not all the programs referencing it.
A similar benefit is available for actions as well. If you have a complex set of actions, for example running all of the sprinklers in different stages, you could save that in one program called 'Water Lawn'. Other programs can be written to start the sprinklers, on schedule, or when a button is pressed for example.