The Companion Specification has been designed from the outset for use in both greenfield (new machines) and brownfield (existing machines). At the same time, important control system manufacturers have also been involved and their views on the retrofitting of existing machines have been taken into account.

It will now be possible to upgrade existing machines up to a certain age directly with retrofit solutions from the manufacturers. At the same time, there will also be third-party solutions to address special cases.
It should be noted, however, that the full scope of the specification can certainly not be fulfilled. But this is exactly what so-called profiles have been defined for, in order to be able to make a clear statement about the degree of fulfilment.