Just like the industrial society of the last century depended on natural resources, today society depends on information and its exchange. Semantic Web technologies address the problem of information complexity by providing advanced support for representing and processing distributed information, while peer-to-peer technologies address issues of system complexity by allowing flexible and decentralized information storage and processing. Systems that are based on Semantic Web and peer-to-peer technologies promise to combine the advantages of the two mechanisms. A peer-to-peer style architecture for the Semantic Web will avoid both physical and semantic bottlenecks that limit information and knowledge exchange. Staab and Stuckenschmidt structured the selected contributions into four parts: Part I, Data Storage and Access, prepares the semantic foundation, i.e. data modelling and querying in a flexible and yet scalable manner. These foundations allow for dealing with the organization of information at the individual peers. Part II, Querying the Network, considers the routing of queries, as well as continuous queries and personalized queries under the conditions of the permanently changing topological structure of a peer-to-peer network. Part III, Semantic Integration, deals with the mapping of heterogeneous data representations. Finally Part IV, Methodology and Systems, reports experiences from case studies and sample applications. The overall result is a state-of-the-art description of the potential of Semantic Web and peer-to-peer technologies for information sharing and knowledge management when applied jointly. It serves researchers in academia and industry as an excellent and lasting reference and source of inspiration.