The Sims and the Sims 2 have always used the so-called Simantics scripting, which define the behaviour of objects and Sims. A somewhat old article, from the Game Developers Conference a few months ago, gives an introduction through Simantics and Edith, the program used to program the scripts. The scripting is explained, and a few pictures showing Edith are there as well. You can read the article at GameDev.