This book systematically identifies the lack of methodological support for development of requirements and software architecture in the state-of-the-art. To overcome this deficiency, the QuaDRA framework is proposed as a problem-oriented approach. It provides an instantiation of the Twin Peaks model for supporting the intertwining relationship of requirements and software architecture. QuaDRA includes several structured methods which guide software engineers in quality- and pattern-based co-development of requirements and early design alternatives in an iterative and concurrent manner. pp