Notation3 as an Existential Rule Language

Dörthe Arndt, Stephan Mennicke

Abstract: Notation3 Logic ( $$\text {N}_3$$ ) is an extension of RDF which allows the user to write rules introducing new blank nodes to RDF graphs. Many applications (e.g., ontology mapping) rely on this feature as blank nodes – used directly or in auxiliary constructs – are omnipresent on the Web. However, the number of fast $$\text {N}_3$$ reasoners fully supporting blank node introduction is rather limited. On the other hand, there are engines like VLog or Nemo not directly supporting Semantic Web rule formats but developed for very similar constructs: existential rules. In this paper we investigate the relation between $$\text {N}_3$$ rules with blank nodes in their heads and existential rules. We identify a subset of $$\text {N}_3$$ which can be mapped directly to existential rules and define such a mapping preserving the equivalence of $$\text {N}_3$$ formulae. To also illustrate that $$\text {N}_3$$ reasoning could benefit from our translation, we employ this mapping in an implementation to compare the performance of the $$\text {N}_3$$ reasoners EYE and cwm to VLog and Nemo on $$\text {N}_3$$ rules and their mapped counterparts. Our tests show that the existential rule reasoners perform particularly well for use cases containing many facts while the EYE reasoner is very fast when dealing with a high number of dependent rules. We thus provide a tool enabling the Semantic Web community to directly use existing and future existential rule reasoners and benefit from the findings of this active community.