Aggregate Queries in Peer-to-Peer OLAP

Abstract

A peer-to-peer (P2P) data management system consists essentially of a network of peer systems, each maintaining full autonomy over its own data resources. Data exchange between peers occurs when one of them, in the role of a local peer, needs data available in other nodes, denoted the acquaintances of the local peer. No global schema is assumed to exist for any data under this computing paradigm. Henceforth, data provided by an acquaintance of a local peer must be adapted, in a manner that answers to queries posed by local peer users conform the view those users have of their data. Because a multidimensional database normally consists in a collection of views of aggregated data, a careful translation process is needed in this case, in order to transform any summary concept that appears in a peer acquaintance into a summary concept meaningful to the requesting peer. We present a model for multidimensional data distributed in a P2P network, and a query rewriting technique, that allows a local peer to propagate OLAP queries among its acquaintances, obtaining a meaningful and correct answer.