StateCharts (Harel, 1987) is a visual formalism for declarative description of complex interactive systems. It extends the conventional state machine formalism with Hierarchy, Concurrency and Communication.

SCXML is a W3C standard based on StateCharts. This is a C++ library that implements the SCXML specification. Instead of XML, a StateChart is represented as a StateChart protobuf.

Many features from the SCXML standard have been implemented.

• Composite State
• Parallel State
• Datamodel
• Transitions (Conditional, Eventless)
• Executable Statements (Raise, Log, Assign, If, ForEach, Send)
• Serialize/Deserialize the state machine

• History

Here's an example of a StateChart that describes a Microwave.

You can see //statechart/example/microwave_example_main.cc for details on how to specify such a StateChart as a StateChart proto and how to use it in code.

To build the library you'll need bazel. You can download and install it from here.

# Download/Clone the repo.
git clone https://github.com/google/statechart.git
cd statechart

# Build the library
bazel build //statechart/...

# Run unit tests
bazel test //statechart/...

# Run the Microwave example
bazel run //statechart/example:microwave_example_main -- --alsologtostderr

This is not an officially supported Google product.

• David Harel, 1987, Statecharts: a visual formalism for complex systems, Science of Computer Programming. Link
• State Chart XML (SCXML): State Machine Notation for Control Abstraction. Link