Safe Query Processing for Pairwise Authorizations in Coalition Networks

In a coalition network where database servers of multiple parties are linked to facilitate information sharing, a data owner usually wants to authorize different portions of its information, in an antonomous way, to be accessible by different peer parties; consequently, each party has a distinct authorized view over the data stored in the coalition network. The requirements, however, impose new challenges on safe query evaluation, because query planning has to resolve the view discrepancy between parties due to the independently defined authorizations, ensuring each server does not receive data it is not authorized to see, and meanwhile guarantees correct query results. We present an algorithm that, given a set of authorizations and a query plan, generates a safe execution strategy. The algorithm enables per-party access authorization and autonomous access control. Following the principle of efficient distributed computation, it explicitly supports distributed query evaluation. A new join method, named split-join, is proposed, significantly reducing the inter-server data transmission cost by pushing the join computation as close as to the data sources. The proofs of the correctness and safety of the algorithm are presented. The performance evaluation result is reported.