What distinction is crucial when separating the conceptual breakthrough at PARC from the functional UI toolkit?

Answer

Inventing the graphical elements versus inventing the software structure (API/library).

It is vital to distinguish between inventing the *graphical elements* (like the concept of a window) and inventing the *software structure* (the API or library) needed to manage those elements consistently across applications.

What distinction is crucial when separating the conceptual breakthrough at PARC from the functional UI toolkit?
inventionsoftwareinventorInterfacetoolkit