{"type":"ScholarlyArticle","title":"The Impact of Disjunction on Query Answering Under Guarded-Based Existential Rules","authors":[{"name":"Pierre Bourhis","slug":"pierre-bourhis","given":"Pierre","family":"Bourhis","affiliation":""},{"name":"Michael Morak","slug":"michael-morak","given":"Michael","family":"Morak","affiliation":""},{"name":"Andreas Pieris","slug":"andreas-pieris","given":"Andreas","family":"Pieris","affiliation":""}],"abstract":"We study the complexity of conjunctive query answering under (weakly-)(frontier-)guarded disjunctive existential rules, i.e., existential rules extended with disjunction, and their main subclasses, linear rules and inclusion dependencies (IDs). Our main result states that conjunctive query answering under a fixed set of disjunctive IDs is 2EXPTIME-hard. This quite surprising result together with a 2EXPTIME upper bound for weakly-frontier-guarded disjunctive rules, obtained by exploiting recent results on guarded negation first-order logic, gives us a complete picture of the computational complexity of our problem. We also consider a natural subclass of disjunctive IDs, namely frontier-one (only one variable is propagated), for which the combined complexity decreases to EXPTIME. Finally, we show that frontier-guarded rules, combined with negative constraints, are strictly more expressive than DL-LiteHbool, one of the most expressive languages of the DL-Lite family. We also show that query answering under this DL is 2EXPTIME-complete in combined complexity.","doi":null,"url":"https://ijcai.org/proceedings/2013/124","pdf":"https://ijcai.org/proceedings/2013/0124.pdf","markdown":"https://ijcai.org/proceedings/2013/124.md","bibtex":"https://ijcai.org/proceedings/2013/bibtex/124","volume":{"slug":"2013","title":"Proceedings of the Twenty-Third International Joint Conference on Artificial Intelligence","short_title":"IJCAI 2013","url":"https://ijcai.org/proceedings/2013/","year":2013,"location":"Beijing, China","dates":"3–9 August 2013","editors":"Francesca Rossi","isbn":"978-1-57735-633-2","publisher":"AAAI Press / International Joint Conferences on Artificial Intelligence","doi_prefix":""},"section":null,"track":"","number":124,"pages":{"first":796,"last":801},"keywords":[],"videos":[],"references":[],"license_note":"Copyright International Joint Conferences on Artificial Intelligence."}