In the 1990s, Professor Iwao Kobayashi published his book 20 Keys to Workplace Improvement and created a practical, step-by-step improvement framework called "the 20 Keys". He identified 20 operations focus areas which should be improved to attain holistic and sustainable change. He went further and identified the 5 levels of implementation for each of these 20 focus areas. 4 of the focus areas are called Foundation Keys. According to the 20 Keys, these foundation keys should be launched ahead of the others in order to form a strong constitution in the company. The four foundation keys are: