Affordances, those features of a product that help you figure out how to use it, are relative.
Most of the busses in the Kitchener-Waterloo region have rear doors that open when you wave your hand in front of them. The one I took downtown this morning must have been an older model because it just had two vertical push bars on the doors.
When we arrived at the terminal, the young woman at the front of the queue to get off started to wave her hands in front of the door, which did not respond. Puzzled and alarmed, she began to shout at the driver to open the doors, until someone behind her said, “push the handle”.
“Oh,” she said, chagrined, before she hurried off into the crowd.
Door handles are a common textbook example of affordances. But affordances, it seems, are relative.
We talk a lot about making interfaces intuitive. But intuitive simply means, corresponds to my intuition. And my intuition simply means my guess based on how other stuff I use works.
Intuitive is relative.
Which is why the need for documentation will not disappear entirely from the earth, but also why our standards for what needs to be documented have to change over time.
Documentation fills the gaps left by affordances and intuition. They are relative, and documentation must be too.