Inverse Roles Make Conjunctive Queries Hard
نویسنده
چکیده
Conjunctive query answering is an important DL reasoning task. Although this task is by now quite well-understood, tight complexity bounds for conjunctive query answering in expressive DLs have never been obtained: all known algorithms run in deterministic double exponential time, but the existing lower bound is only an EXPTIME one. In this paper, we prove that conjunctive query answering in ALCI is 2-EXPTIME-hard (and thus complete), and that it becomes NEXPTIME-complete under some reasonable assumptions.
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Two Upper Bounds for Conjunctive Query Answering in SHIQ
We have shown recently that, in extensions of ALC that involve inverse roles, conjunctive query answering is harder than satisfiability: it is 2-ExpTime-complete in general and NExpTime-hard if queries are connected and contain at least one answer variable [10]. In this paper, we show that, in SHIQ without inverse roles (and without transitive roles in the query), conjunctive query answering is...
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