Nicolas Markey

Abstract

QCTL extends the temporal logic CTL with quantification over atomic propositions. While the algorithmic questions for QCTL and its fragments with limited quantification depth are well-understood (e.g. satisfiability of QCTLk, with at most k nested blocks of quantifiers, is k+1-EXPTIME-complete), very few results are known about the expressiveness of this logic. We address such expressiveness questions in this paper. We first consider the distinguishing power of these logics (i.e., their ability to separate models), their relationship with behavioural equivalences, and their ability to capture the behaviours of finite Kripke structures with so-called characteristic formulas. We then consider their expressive power (i.e., their ability to express a property), showing that in terms of expressiveness the hierarchy QCTLk collapses at level 2 (in other terms, any QCTL formula can be expressed using at most two nested blocks of quantifiers).

@inproceedings{concur2016-DLM,
  author =              {David, Am{\'e}lie and Laroussinie, Fran{\c c}ois and
                         Markey, Nicolas},
  title =               {On~the expressiveness of~{QCTL}},
  editor =              {Desharnais, Jules and Jagadeesan, Radha},
  booktitle =           {{P}roceedings of the 27th {I}nternational
                         {C}onference on {C}oncurrency {T}heory
                         ({CONCUR}'16)},
  acronym =             {{CONCUR}'16},
  publisher =           {Leibniz-Zentrum f{\"u}r Informatik},
  series =              {Leibniz International Proceedings in Informatics},
  volume =              {59},
  pages =               {28:1-28:15},
  year =                {2016},
  month =               aug,
  doi =                 {10.4230/LIPIcs.CONCUR.2016.28},
  abstract =            {QCTL extends the temporal logic CTL with
                         quantification over atomic propositions. While the
                         algorithmic questions for QCTL and its fragments
                         with limited quantification depth are
                         well-understood (e.g. satisfiability of
                         QCTL\textsuperscript{\(k\)}, with at most \(k\)
                         nested blocks of quantifiers, is
                         \(k+1\)-EXPTIME-complete), very few results are
                         known about the expressiveness of this logic.
                         We~address such expressiveness questions in this
                         paper. We first consider the \emph{distinguishing
                         power} of these logics (i.e.,~their ability to
                         separate models), their relationship with
                         behavioural equivalences, and their ability to
                         capture the behaviours of finite Kripke structures
                         with so-called characteristic formulas. We then
                         consider their \emph{expressive power} (i.e.,~their
                         ability to express a property), showing that in
                         terms of expressiveness the hierarchy
                         QCTL\textsuperscript{\(k\)} collapses at level~2
                         (in~other terms, any~QCTL formula can be expressed
                         using at most two nested blocks of quantifiers).},
}