Architecture , interaction , systems

"I go up", said the elevator, "or down." "Good," said Zaphod, "We're going up." "Or down," the elevator reminded him. "Yeah, OK, up please." There was a moment of silence. "Down's very nice," suggested the elevator hopefully. "Oh yeah?" "Super." "Good," said Zaphod, "Now will you take us up?" "May I ask you," inquired the elevator in its sweetest, most reasonable voice, "if you've considered all the possibilities that down might offer you?"