Available PhD studentship in database theory

The PhD topic is in the area of foundations of data management, focusing on querying inconsistent data.

Data management systems nowadays need to handle large data sets often containing inconsistent or incomplete information, and yet guarantee the relevance of query answers. New techniques are needed for making data access more reliable, and new tools are required for making data querying more efficient in this context.

The main focus of the PhD will be the study of consistent query answering. In this scenario the data set may have inconsistencies relative to integrity constraints (e.g., key and foreign key constraints, functional dependencies, inclusion constraints, etc.). Queries issued on the database need to be answered despite the inconsistencies. The goal is to provide only consistent answers, i.e. answers that can be be found after virtually repairing the database to remove inconsistencies. As many repairs may exist for a given database, the widely accepted notion is the one of certain answers, i.e. answers that can be found in all possible database repairs.

The challenge is then to provide efficient algorithms for computing certain answers directly from the inconsistent database, as going through all possible repairs is clearly unfeasible. Particularly attractive is the possibility of obtaining certain answers by query rewriting, i.e. by issuing on the inconsistent database a new query with good computational properties. Despite a rich literature on the topic (see [1,2,3] for instance) many questions remain open even for simple classes of queries and constraints, such as conjunctive queries and primary key constraints.