Section: New Results

Distributed data management

Participants : Serge Abiteboul, Émilien Antoine, Cristina Sirangelo.

We have studied the feasibility of query answering in the presence of incomplete information in data. In particular we have investigated when it is the case that classical query evaluation techniques, which are commonly used over complete data, suffice to answer queries also in the presence of incompleteness [26] . These results allowed to find syntactic classes of queries that can be answered efficiently under many well known semantics of incompleteness, using query answering techniques which are already implemented (and optimized) in classical database systems.

The management of Web users' personal information is increasingly distributed across a broad array of applications and systems, including online social networks and cloud-based services. While users wish to share and integrate data using these systems, it is increasingly difficult to avoid the risks of unintended disclosures or unauthorized access by applications.

In [21] , [20] , we propose a novel access control model that operates within a distributed data management framework based on datalog. Using this model, users can control access to data they own and control applications they run. They can conveniently specify access control policies providing flexible tuple-level control derived using provenance information. We present a formal specification of the model, a theoretical analysis, and an implementation. We show that the computational cost of access control is acceptable.