Embedded within the methods and tools of Lean is the activity-driving kaizen event, a focused, waste-eliminating productivity improvement activity. Most of the Lean literature discusses seven major sources of waste: overproduction, excess inventory, waiting time, transportation, excess motion, defects, and overprocessing. The best way to understand the essence of a Lean process is to know what it attempts to eliminate: waste. In today's global economy, elimination of waste is also a company survival necessity. When a process mapping exercise of a product is completed and activities are classified, the result is that there are value-added steps, steps that are "absolute waste," steps that are "wasteful but temporarily necessary," and steps that call "administratively necessary''. Absolute waste is what should be removed from any Lean process as soon as possible—some may be considered wasteful but temporarily necessary in the short term. These were forms of waste identified and singled out for elimination by Taiichi Ohno in his writings.