Richard Schechner remembers the real-life side of interaction.
Chris Crawford adduces the algorithms of games against dramatic conventions.
Nick Montfort argues that the contentious notion of the "player character" usefully constrains and makes possible the player's interaction with the gameworld. He considers the possibility that in interactive fiction one plays the character (like an actor plays a role) rather than playing the game.
The builder of Façade, an "interactive story world," Michael Mateas offers both a poetics and a neo-Aristotelian project (for interactive drama and games).
Bryan Loyall cites expertly paced penguins in this response to Janet Murray.