How exactly is the major league baseball schedule determined each year?

For the past 24 years, MLB outsourced the task of scheduling to the husband-and-wife team of Henry and Holly Stephenson. But for 2005, MLB has hired a Pittsburgh-based firm, the Sports Scheduling Group, to replace the Stephensons. Apparently, MLB hopes to avoid so many "semi-repeaters" in which the same teams play in back-to-back series at home then away.