Metamodel 2: Requirements for Replacing a Legacy System

The client for this metamodel was the requirements team at a large telecommunications company. The company needed to replace a major legacy system that had been built by an outside organization. Because the system had been used for so many years, had grown so large, and had undergone many enhancements, no single person in the company understood all of its functionality. The group needed a mechanism to capture the information from many subject matter experts as to the current functionality, its rules, and its constraints. In addition, deficiencies of the current system needed to be understood. A "Function/Task Flow Model" was developed to capture enough detail about the "as-is" system to ensure that no requirements would slip through the cracks.

Once all the current functionality was understood, the business could make judgments about what needed to be kept, what could be dropped, and what should be added. "To-be" models were then built. With these as a basis, the next step was to derive textual requirements - data-oriented, functional and non-functional. The group then worked together with business owners and development to assess both the business priority and the technical difficulty of each requirement, and to assign requirements to project increments. Requirement status was tracked throughout the life of the project.