Tuple-Generating Dependencies Capture Complex Values

We formalise a variant of Datalog that allows complex values constructed by nesting elements of the input database in sets and tuples. We study its complexity and give a translation into sets of tuple-generating dependencies (TGDs) for which the standard chase terminates on any input database. We identify a fragment for which reasoning is tractable. As membership is undecidable for this fragment, we develop decidable sufficient conditions. 2012 ACM Subject Classification Theory of computation → Complexity theory and logic; Theory of computation → Constraint and logic programming; Theory of computation → Logic and databases Acknowledgements We would like to thank the anonymous reviewers for their detailed feedback that led to this revised version of the paper.