Book excerpt: This book constitutes the thoroughly refereed post-proceedings of the 6th Thematic Workshop of the EU Network of Excellence DELOS on Digital Library Architectures, held in Cagliari, Italy, in June 2004. The 15 revised full papers presented were carefully reviewed. The subjects covered include: service grids for scientific applications, distributed digital libraries, grid computing, peer-to-peer networks, service oriented architectures for digital libraries, a distributed digital library for support of community radios, multimedia management and search, query trading and processing, metadata management, retrieval functionality, and personalization services.