Loop restricted existential rules and first-order rewritability for query answering

Abstract

Under the language of TGDs, queries are answered against an ontology represented by a set of TGDs and an input database. In particular, given a database instance D, a finite set ∑ of TGDs, and a query q, we want to decide whether D U ∑= q. However, this problem is undecidable generally, due to the potential cyclic applications of TGDs in