Defeasible Inclusions in Low-Complexity DLs: Preliminary Notes

Piero A. Bonatti, Marco Faella, Luigi Sauro

Abstract: We analyze the complexity of reasoning with circumscribed low-complexity DLs such as DL-lite and the EL family, under suitable restrictions on the use of abnormality predicates. We prove that in circumscribed DL-liteR complexity drops from NExpNP to the second level of the polynomial hierarchy. In EL, reasoning remains ExpTime-hard, in general. However, by restricting the possible occurrences of existential restrictions, we obtain membership in Σ2p and Π2p for an extension of EL.