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PRISM is a probabilistic model checker, a tool for formal modelling and analysis of systems that exhibit random or probabilistic behaviour. It supports a wide range of probabilistic models and has been used to analyse systems from many different application domains, including communication and multimedia protocols, randomised distributed algorithms, security protocols, biological systems and many others.

Example PRISM graph PRISM supports several types of probabilistic models:

  • discrete-time Markov chains (DTMCs)
  • continuous-time Markov chains (CTMCs)
  • Markov decision processes (MDPs)
  • probabilistic automata (PAs)
  • probabilistic timed automata (PTAs)
plus extensions of these models with costs and rewards.

Models are described using the PRISM language, a simple, state-based language. PRISM provides support for automated analysis of a wide range of quantitative properties of these models, e.g. "what is the probability of a failure causing the system to shut down within 4 hours?", "what is the worst-case probability of the protocol terminating in error, over all possible initial configurations?", "what is the expected size of the message queue after 30 minutes?", or "what is the worst-case expected time taken for the algorithm to terminate?". The property specification language incorporates the temporal logics PCTL, CSL, LTL and PCTL*, as well as extensions for quantitative specifications and costs/rewards.

PRISM incorporates state-of-the art symbolic data structures and algorithms, based on BDDs (Binary Decision Diagrams) and MTBDDs (Multi-Terminal Binary Decision Diagrams) [KNP04b, Par02]. It also includes a discrete-event simulation engine, providing support for approximate/statistical model checking, and implementations of various different analysis techniques, such as quantitative abstraction refinement and symmetry reduction.

PRISM is free and open source, released under the GNU General Public License (GPL).

To cite PRISM, please use the most recent tool paper, from CAV'11:

  • [KNP11] Marta Kwiatkowska, Gethin Norman and David Parker. PRISM 4.0: Verification of Probabilistic Real-time Systems. In Proc. 23rd International Conference on Computer Aided Verification (CAV’11), volume 6806 of LNCS, pages 585-591, Springer, 2011.

Latest News

July 2011: To coincide with the recent release of PRISM 4.0, we are pleased to announce the new PRISM benchmark suite, for testing or evaluating probabilistic model checking tools and techniques.
July 2011: Congratulations to Shinji Kikuchi and Yasuhide Matsumoto from Fujitsu, who won the Best Paper award for their new paper applying PRISM to cloud computing systems.
May 2011: The final beta release of PRISM 4.0, which includes support for probabilistic timed automata (PTAs) and statistical model checking, is available on the main download page.
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