Project management is delivering product or processes on time. The key though is DELIVERING and delivering WHAT. If the WHAT is not clearly defined, how does anyone, but especially management or the business, know if what was delivered was correct? The WHAT of course is what is to be delivered. The WHAT should be clearly defined as requirements that can be measured and agreed to by all stakeholders. Without a clearly defined WHAT, the potential for project management hell greatly increases. The need therefore is to outline in high level terms, what the project is expected to accomplish. The requirements document would then be used to outline the details and how these details would be measured. This measurement for success would be used to focus the work on the important aspects that have the potential to deliver real value to the business.