An interesting article on cell model creation for statistical timing analysis

Meeting timing at the worst or best-case corner can be very challenging, lengthening design schedules and negatively impacting power consumption. With a large range of potential delay values, often with a difference of as much as 50 percent or more between the slow and fast process corners, it becomes harder to meet both setup times at the worst-case corner and hold times at the best-case corner.

Read the remaining portion of the interesting article at..
http://www.eetimes.com/showArticle.jhtml?articleID=190100003