An affordance is a relationship between the
properties of an object and the capabilities of the
agent that determine just how the object could
possibly be used.
Think of each action by the user as an attempt to step in
the right direction; an error is simply an action that is
incompletely or improperly speciﬁed. Try support, not to
ﬁght, the user's responses. Design explorable systems.
When I say hypertext, I mean the simultaneous
presentation of information and controls
such that the information becomes the
affordance through which the user (or automaton)
obtains choices and selects actions
Roy T. Fielding 2008