Answering Queries with Negation over Existential Rules

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Answering Queries with Negation over Existential Rules

Vortrag von Stephan Mennicke
Ontology-based query answering with existential rules is well understood and implemented for positive queries, in particular conjunctive queries. The situation changes drastically for queries with negation, where there is no agreed-upon semantics or standard implementation. Stratification, as used for Datalog, is not enough for existential rules, since the latter still admit multiple universal models that can differ on negative queries. We, therefore, propose universal core models as a basis for meaningful (non-monotonic) semantics for queries with negation. Since cores are hard to compute, we identify syntactic descriptions of queries that can equivalently be answered over other types of models. This leads to fragments of queries with negation that can safely be evaluated by current chase implementations. We establish new techniques to estimate how the core model differs from other universal models, and we incorporate our findings into a new reasoning approach for existential rules with negation.

The talk is about an upcoming publication in AAAI 2022 by Stefan Ellmauthaler, Markus Krötzsch, Stephan Mennicke

The talk is online,