On The Debt Ceiling; What’s The Baseline?

While it’s “great” that our leaders are debating raising the ceiling, the problem I have is there is not a set baseline. Is it spending levels based on 2008, or is the baseline going to be on the amount of taxes and other revenues the Federal Government takes in? Or is the baseline¬† it going to based on the projected amount for fiscal 2010? To me it would be pretty simple, you start the talks with the goal being to get our spending in line with what we take in.
There are plenty of people writing about the deals that are being talked about, but I have seen very few talking about what the baseline should be.