Blocking Automata for PSPACE DLs

In Description Logics (DLs), both tableau-based and automata-based algorithms are frequently used to show decidability and complexity results for basic inference problems such as concept satisfiability. Whereas tableau-based algorithms usually yield worst-case optimal algorithms in the case of PSpace-complete logics, it is often very hard to design optimal tableau-based algorithms for ExpTime-complete DLs. In contrast, the automata-based approach is usually well-suited to prove ExpTime upper-bounds, but its direct application will usually also yield an ExpTime-algorithm for a PSpace-complete logic since the (tree) automaton constructed for a given concept is usually exponentially large. In the present paper, we formulate conditions under which an on-the-fly construction of such an exponentially large automaton can be used to obtain a PSpace-algorithm. We illustrate the usefulness of this approach by proving a new PSpace upper-bound for satisfiability of concepts w.r.t. acyclic termi...

• Type: Conference
• Year: 2007
• Where: DLOG
• Authors: Franz Baader, Jan Hladik, Rafael Peñaloza
• Keywords: Automated Reasoning, DLOG 2007, Optimal Tableau-based Algorithms, Pspace-complete Logic, Tableau-based Algorithms