In 1995 IBM assembled the OPS team to design, develop, and implement a best of breed single central planning engine (CPE) to support all key decisions to manage the demand supply network for firms that produce semiconductor based packaged goods. Over the 10 year period from 1995 to 2005 the CPE gained recognition as setting a new standard for function and enabling a far more dynamic central planning process creating a more responsive firm which an end to "warring" nations. During this period, the CPE was fully implemented in IBM and Analog Devices receiving awards from both for its business impact. Additionally, its technical achievement was recognized by INFORMS as an Edelman finalist and Wagner winner. Today the CPE remains in use on a daily basis in both firms establishing the standard for best in class function and serves as the base for the next generation CPE. All three authors were key members of the CPE team. This first portion of the presentation provides a 20 year prospective on the CPE covering its development, core function, and an emphasis on the dynamics between the "model" and the planners - that is observation from the trenches. These observation will cover items such as: the importance and complexity of time (date effective, dynamic time buckets, and shutdown days); ever changing views of optimal by planners; how to help a planner who sees his demand supply network as BOM chain understand its representation in equation, how to help an person who knows LP through Excel understand LP as data structures; mixing and matching LP and heuristics, how planners user the model; the model is just the start of the process, not the end; the challenge of lot sizing, a plan is not a schedule; the illusion of pegging; and facilitating a change in process. The second portion will cover near term challenges that next generation CPE's are now working on to support such as: the illusion of capacity, repairing a plan, the illusion of pegging, analytics to support planners as they review plans, faster solutions, the changing boundary between planning and scheduling and other topics.