The way system engineering typically works is that your use cases are developed in what we call an MBSE, which is a model-based system engineering tool. Let's say your MBSE tool is MagicDraw. First, you would get and develop a system spec from your customer requirement specifications. Then your requirements engineers would further derive the system spec and set it up in your DOORS environment. Then your architects would start architecting and modeling from that system spec and develop use cases and logic flow diagrams. Then, as those use cases mature, they turn into performance requirements or constraints to help establish your sequence diagrams. The use cases aren't managed in DOORS, they're managed in an MBSE tool, but like I said, the use cases derive requirements that get put into DOORS.