Why reuse-based process model is essential to have two separate requirements engineering activities in the process?

Answer 1

To make the reuse software engineering a complete model we need to add two more activities of the software process because if we look at the process stages of reuse engineering it starts at component analysis and then Requirement modification. So we need to have Requirements before being able to modify it. In other words how can we modify a requirement before establishing a requirements and also same is true for validation because at the end the system is required to be validated before delivery.