Checking query completeness over incomplete data

We study the problem of query completeness (QC) over partially complete databases. Query completeness is an important goal of data quality assurance. Incomplete databases can occur in many contexts, especially whenever many users are supposed to insert data into the same database. Although the overall data can often not be guaranteed to be complete, some information may exist about completeness of parts of the data, e.g., completeness of parts of tables. Given a query, the question arises whether that information implies that the query returns the same set of answers over the available data as it would over the complete database.