The next design phase is detailed design. Here, you reduce the HLD to imple- mentable form by detailing the functions, specifying the class state machines, andproducing the finished design. Some of the HLD concepts might be unimple. mentable, while others could be unsound. You could see reuse opportunities, have performance insights, and think of integration and system testing issues. Becalhe these changes can impact the requirements and HiD, neither the requirements to the HLD can be considered firm until you have completed the DLD.