Sismic user manual


Statecharts are a well-known visual modeling language for specifying the executable behavior of reactive event-based systems. The essential complexity of statechart models solicits the need for advanced model testing and validation techniques. Sismic is a statechart library for Python providing a set of tools to define, validate, simulate, execute and test statecharts. Sismic is a recursive acronym that stands for Sismic Interactive Statechart Model Interpreter and Checker.

Sismic is mainly developed by Dr. Alexandre Decan as part of his research activities at the Software Engineering Lab of the University of Mons. Sismic is released as open source under the GNU Lesser General Public Licence version 3.0 (LGPLv3).

The scientific article A method for testing and validating executable statechart models, published in 2018 in the Springer Software & Systems Modeling journal, describes the method and techniques for modeling, testing and validating statecharts, as supported by Sismic.


Sismic provides the following features:

  • An easy way to define and to import statecharts, based on the human-friendly YAML markup language

  • A statechart interpreter offering a discrete, step-by-step, and fully observable simulation engine

  • Fully controllable simulation clock, with support for real and simulated time

  • Built-in support for expressing actions and guards using regular Python code, can be easily extended to other programming languages

  • A design-by-contract approach for statecharts: contracts can be specified to express invariants, pre- and postconditions on states and transitions

  • Runtime checking of behavioral properties expressed as statecharts

  • Built-in support for behavior-driven development

  • Support for communication between statecharts

  • Synchronous and asynchronous executions

  • Statechart visualization using PlantUML

The semantics of the statechart interpreter is based on the specification of the SCXML semantics (with a few exceptions), but can be easily tuned to other semantics. Sismic statecharts provides full support for the majority of the UML 2 statechart concepts:

  • simple states, composite states, orthogonal (parallel) states, initial and final states, shallow and deep history states

  • state transitions, guarded transitions, automatic (eventless) transitions, internal transitions and transition priorities

  • statechart variables and their initialisation

  • state entry and exit actions, transition actions

  • internal and external events, parametrized events, delayed events


The Sismic library for Python is mainly developed by Alexandre Decan at the University of Mons with the help of many contributors.

Sismic is released publicly under the GNU Lesser General Public Licence version 3.0 (LGPLv3).

The source code is available on GitHub:

Use GitHub’s integrated services to contribute suggestions and feature requests for this library or to report bugs.

You can cite the research article (PDF) describing the method and techniques supported by Sismic using:

   author = {Mens, Tom and Decan, Alexandre and Spanoudakis, Nikolaos},
   journal = {Software and Systems Modeling},
   publisher = {Springer},
   year = 2018,
   title = {A method for testing and validating executable statechart models},
   doi = {10.1007/s10270-018-0676-3},
   url = {},

You can cite the Sismic library itself using:

    title = "Sismic—A Python library for statechart execution and testing",
    journal = "SoftwareX",
    volume = "12",
    pages = "100590",
    year = "2020",
    issn = "2352-7110",
    doi = "10.1016/j.softx.2020.100590",
    url = "",
    author = "Alexandre Decan and Tom Mens",


  author = {Decan, Alexandre},
  title = {Sismic Interactive Statechart Model Interpreter and Checker},
  url = {},