Bravo! Another proponent of data-driven dispatch.

"... in practice, this is equivalent to executing a set of short-circuit conditionals ... but it's cleaner, and you can make each Command much more complex than the body of a sensible conditional."

This approach has the tendency to scare off some programmers, since the state machine engine's code is completely independent from the data which defines the state-machine, but once you have your hands around the concept, the ease with which fundamental changes to the logic may be made justifies the learning curve.

If one is not careful with this approach, it is easy to end up with Write-Only code, however.

dmm