Controllers, on the other hand, may reformat or manipulate data because controllers do not aim to be reusable; they instead aim to do as good a job as possible at a particular task.
For example, a function named Get-DiskInfo would return disk sizing information in bytes, because that’s the most-granular unit of measurement the operating system offers. A controller that was creating an inventory of free disk space might translate that into gigabytes, because that unit of measurement is the most convenient for the people who will view the inventory report.
An intermediate step is useful for tools that are packaged in script modules: views. By building a manifest for the module, you can have the module also include a custom .format.ps1xml view definition file. The view can specify manipulated data values, such as the default view used by PowerShell to display the output of Get-Process. The view does not manipulate the underlying data, leaving the raw data available for any purpose.