This book constitutes the thoroughly refereed post-proceedings of the International Dagstuhl-Seminar on Architecting Systems with Trustworthy Components, held in Dagstuhl Castle, Germany, in December 2004. Presents 10 revised full papers together with 5 invited papers contributed by outstanding researchers. Discusses core problems in measurement and normalization of non-functional properties, modular reasoning over non-functional properties, capture of component requirements in interfaces and prools, interference and synergy of top-down and bottom-up aspects, and more.