This collection of top-notch articles by well-known experts brings together, for the first time, key elements of this area that are fast becoming the focus of much current research and practice in computing. About half the articles deal with theoretical frameworks, models, and systems of notation; the rest comprise case studies by architects of prototype systems who present findings on architectures verification. The emphasis is on advances in the technological infrastructure of component-based systems; how to design and specify reusable components; and how to reason about, verify, and validate systems from components. An introduction by Clemens Szyperski gives a snapshot of current research in the field.