Draw length?

[Taxfrog]

I've seen some differing rules of draw length on the internet. Some say 1.75-2" from the deepest part of the belly of the bow, some say directly on the back of the bow. For a flatbow, where do we measure 28"? Is it where the drawstop touches the back? Or is it some measurement from the belly?

[Cyric]

From the draw stop or back of the arrow to where the string goes in the nock.