How do I get to the specific requirements of a complex problem?

To analyze a complex problem try using functional decomposition. Begin by identifying the highest-level function, then break it into its component functions. Break those sub-functions into their processes, and finally, break each process into its sub-processes.

If you ever find yourself needing to understand a problem or solution in deeper detail, you can often get a head start by consulting the requirements management plan, which should show you how the requirements are allocated (or assigned) to functions, sub-functions, processes, and sub-processes. In fact, this is a very good argument for creating a requirements management plan in the first place—to document how the requirements are prioritized, sequenced, decomposed, and allocated.