How do I verify that my SCXML defines a valid state machine?

Question

I've just started looking at defining state machines and SCXML looks attractive, especially the Apache Commons SCXML for Java. Obviously I can validate the XML (with an appropriate XSD).

However I can't obviously find any way to verify that the defined state machine is valid (no dead-ends, no unreachable states, etc).

But how can I verify a defined state-machine before I execute it? In particular I am interested in tools that can integrated into a build tool-chain (i.e. from the command-line).

Answer 1

The uscxml-analyze tool from the uSCXML distribution will do just that:

$ uscxml-browser -c ../../test/w3c/ecma/test144.scxml

It checks for a whole bunch of issues:

• Required attributes
• Valid parent elements
• Valid default history configurations
• Valid initial transition
• Valid initial attributes
• Unreachable state hierarchies
• Uniqueness of state id attribute
• Valid targets for transitions
• Redundant / unselectable transitions
• Superfluous history elements
• Legal configuration of target sets
• A bunch of attribute / element combination constraints
• Valid syntax of data-model expressions

The uSCXML interpreter will also check for cycles within a macro-step during interpretation.