How to Judge Grape Ripeness Before Harvest

Grape ripeness is an elusive concept for many people and sometimes an elusive achievement for vineyards. Much of the difficulty with discussions of grape ripeness is that there is often an implied standard, but in reality, ripeness is an entirely subjective judgment. So, there are really two issues to address: 1) how do we define grape ripeness and 2) how do we measure ripeness parameters to assist our harvest decisions.