I find the article so interesting because these guys were amongst the first to consider metaphors for visualising computer tasks. They originated the Graphical User Interface.
There's a really interesting passage describing how the designers hoped to reflect real-life with their "icons":
Although moving a document to a Desktop resource such as a printer involves transferring the document icon to the same square as the printer icon, the printer immediately "absorbs" the document, queuing it for printing. You can leave documents on your Desktop indefinitely, just as on a real desk, or you can file them away in folders or file drawers.
It's amazing how how much more they considered their work as art rather than engineering.
Designing the Star user interface