In Cimple, a joint project between Wisconsin and Yahoo! Research, we are building systems that manage information for online communities. In this paper we discuss the fundamental roles users play in such systems, then the difficult user-centric research challenges raised by these roles, with respect to contributing to the system, accessing and using it, and leveraging the social interaction of users. 1

The peer-to-peer (P2P) paradigm is an intriguing approach for coping with dynamically evolving federations of loosely coupled digital libraries. In addition to the libraries, user agents with powerful personalized tools may participate as peers, too. Such a P2P system promises unlimited scalability, robustness to failures, fluctuation, and load dynamics, and also much reduced vulnerability to attacks and information manipulation. Peers remain autonomous and participate in the P2P system and collaborate on behalf of user requests at their discretion. In a typical scenario, a user peer would utilize its local profile to compile an information demand and issue queries to the library peers that most suitable for the given demand. The decision about where a query should be sent is known as query routing or database selection or resource selection. Previous work on database selection assumed a static architecture with a fairly small a number of data sources. The P2P scenario is different: Peer-to-Peer is large scale and high dynamics such that the disermination, maintenance and effective use of statistical summaries about peers ‘ information content entails difficult questions. � Personal Strategies for query routing based on local knowledge, querylogs, and further user-behavior with other peers provide new opportunities to improve query execution. Digital