The vision of the Piazza peer data management system (PDMS) project is to provide "semantic mediation" between an environment of thousands of peers, each with its own schemas. Rather than requiring the use of a single, uniform, centralized mediated schema to share data between peers, Piazza allows peers to define semantic mappings between pairs of peers (or among small subsets of peers). In turn, transitive relationships among the schemas of the peers are exploited so the entire resources of the PDMS can be used.
The Piazza project arose as a natural evolution of the Sagres system, which focused on coordinating data sharing among ubiquitous computing devices. The ubiquitous computing context looks very similar to a PDMS in which most peers (devices) have limited capabilities and low-power requirements. We believe that the core data management issues can be better studied in the context of peer-to-peer computing.