[ros-users] Current state of SMACH in ROS

[Jonathan Bohren]

On Fri, Feb 17, 2012 at 8:09 AM, Ingo Lütkebohle <iluetkeb at gmail.com> wrote:

> I agree, and we deliberately only use a subset of SCXML's
> functionality, with other features being rejected at design time.
> However, everything that I want to express in a state-machine
> language, I can express in it. That's a very good start, in my
> opinion, and something that is otherwise lacking.
>

Well, I think going to a pure state-machine / state-chart specification
would be a step back. The reason why we created SMACH in the first place
was because in robotics applications and experiments, we often want more
than what just an FSM-equivalent representation would allow us to specify.
Remember, the SMACH semantics are more like a switched hybrid system than a
pure FSM, since the true "state" at any given time is not only the task
state but also the state of the data flowing between the task states. This
was our attempt to increase the amount of an application which was being
strictly modeled in the executive, without putting an unnecessary burden on
the developer. It's a small step forward, but I think it enables us to
achieve a lot more.
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