Among the new inclusions in Revit 2016 R2 is the ability to create Global Parameters. R2 updates are only available to subscribed customers and therefore this functionality will not be available to non-subscribed customers (normal and R2 updates are mutually exclusive).
Global parameters can be used to drive or report the value of one parameter to another parameter, but one cannot access them in element properties (map instance or type parameters of elements to global parameters).
Consider that an architect is given the extents of a building they may design in terms of height and width, but that these quantities initially have an uncertainty included. This means that there would be an advantage to have the height and width driven parametrically. Global parameters of type length are created (note that unlike project parameters they are not associated with categories)
The value of 10 000 mm has been assigned to the width of the building while the formula for the length is set to have the width to length appear in a golden proportion (1 : 1.618).
After the shell of the building has been created, it is dimensioned and labeled with the global parameters just created. If the architect needs to adjust the dimensions later they only need to do is set the value of the parameters as required.
Clicking on the pencil icon on the dimension takes the user directly to the global parameter dialogue. When in the dialogue, a parameter can be shown in the relevant view and it may also be searched for.
Global parameters may can also be made to report their measurement. Wall thickness, for instance, may drive the width and depth of a foundation (as per legal requirements).