That appears to be what has been established between the United States and Iraq in figuring out the future status of American forces in Iraq and when those forces may ultimately be able to come home. For more on this issue, you should make sure to check out this interivew between NBC’s Andrea Mitchell and General David Petraeus:
I can see myself signing on to a plan with “aspirational goals” concerning the future of American troops in Iraq. But hard and fast timetables with dates will only serve to give remaining insurgent and terrorist forces the information they need to wait out American forces and then run rampant once the United States leaves. There must remain significant amounts of flexibility in any plan to allow for adaptations to changes in conditions, as General Petraeus points out in his interview with Andrea Mitchell. The absence of such flexibility will not only make any agreement not worth the paper that it is written on, it will actively work to undermine both American and Iraqi security interests.