The Richard Lazarus and Susan Folkman Model For Stress Developed in 1984, Lazarus stress is defined as an "imbalance between demands and resources." What the two researchers meant by this was that every person has resources and skills available to them. When talking about stress, these skills are known as coping mechanisms. Testing. Operation / deployment. Maintenance. So we can see that the waterfall model works hierarchy from top to bottom, with one phase completed with full verifications and then switching to another phase, including phase processes like Conception, Initiation, Analysis, Design, Construction, Testing, Production/Implementation, and Maintenance.