On the expressiveness and complexity of randomization in finite state monitors

Rohit Chadha, A. Prasad Sistla, Mahesh Viswanathan

Research output: Contribution to journalArticlepeer-review


In this article, we introduce the model of finite state probabilistic monitors (FPM), which are finite state automata on infinite strings that have probabilistic transitions and an absorbing reject state. FPMs are a natural automata model that can be seen as either randomized run-time monitoring algorithms or as models of open, probabilistic reactive systems that can fail. We give a number of results that characterize, topologically as well as with respect to their computational power, the sets of languages recognized by FPMs. We also study the emptiness and universality problems for such automata and give exact complexity bounds for these problems.

Original languageEnglish (US)
Article number1552287
JournalJournal of the ACM
Issue number5
StatePublished - Aug 1 2009


  • Omega automata
  • Probabilistic automata
  • Randomization
  • Runtime verification
  • Topology

ASJC Scopus subject areas

  • Software
  • Control and Systems Engineering
  • Information Systems
  • Hardware and Architecture
  • Artificial Intelligence


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