论文信息 - Undecidability of PDL with L={a^(2i)|i>=0}

Undecidability of PDL with L={a^(2i)|i>=0}

Abstract It is shown that the validity problem for propositional dynamic logic (PDL), which is decidable and actually DEXPTIME-complete for the usual class of regular programs, becomes highly undecidable, viz. Π 1 1 -complete, when the single nonregular one-letter program L = { a 2 i |; i ⩾ 0} is added. This answers a question of Harel, Pnueli, and Stavi.

David Harel | Mike Paterson

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