Sismic user manual


Sismic is a recursive acronym that stands for Sismic Interactive Statechart Model Interpreter and Checker.

The Sismic library for Python (version 3.4 or higher) is mainly developed by Alexandre Decan at the University of Mons.

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

Sismic provides a set of tools to define, validate, simulate, execute and test statecharts. Statecharts are a well-known visual modeling language for representing the executable behavior of complex reactive event-based systems.


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
  • Synchronous and asynchronous simulation, in real time or simulated time
  • Support for communication between statecharts and co-simulation
  • 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, sequential conditions, pre- and postconditions on states and transitions
  • Predefined step definitions and utilities (including test coverage) to support behavior-driven development
  • A unit testing framework for statecharts, including generation of test scenarios

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
  • statechart (scoped) variables and their initialisation
  • state entry and exit actions, transition actions
  • internal and external parametrized events

Source code

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.