REQUIRED: A Tool to Relax Queries through Relaxed Functional Dependencies

Query relaxation aims to relax the query constraints in order to derive some approximate results when the answer set is small. In this demo paper, we present REQUIRED, an automatized, portable, and scalable query relaxation tool leveraging metadata learned from an input dataset. The intuition is to use relationships underlying attribute values to derive a new query whose approximate results still meet the user’s expectations. In particular, REQUIRED exploits relaxed functional dependencies to modify the original query in two different ways: ( 𝑖 ) relaxing some query conditions by replacing the equality constraints with ranges and/or collections of admissible values, and ( 𝑖𝑖 ) rewriting the original query by replacing some or all the attributes involved in the conditions of the query with attributes related to them. Our demonstration scenarios show that REQUIRED is effective in properly relaxing queries according to the considered strategy.