Source: Half-Life Fallout

ModDB has put online it's interview with Rick Ellis, senior engineering lead at Valve, here some words from the interview:

What capabilities does source have for expanding from the FPS genre?

Rick Ellis: Three of the biggest things that Source has to expand the FPS genre are facial expressions/animations, advanced AI and real world physics. The physics engine allows us to build new and very interesting types of game play while the facial expressions allow us to more realistically convey information to the user and help the user feel emotional about the game. The advanced AI will make fighting with teammates better as well as making opponents more realistic and in some cases more difficult.

The full interview can be found here.