I started to study about state transition chart. As I see, it assumes all state transition is done instantly with no time consuming. But in most of my case, I'm heavily depending on asynchronous I/O, so it seems to be less efficient modeling them with the chart.

How do you think about how to represent asynchronous state change? Please recommend something to me :)


2 Answers 2


As far as my knowledge goes for (UML) State diagrams it can't happen. If the state change isn't instantly there is obvious a in between state. In your example a state where your waiting for the IO to complete.

  • 1
    -1 The question is not about state diagrams but state charts.
    – KeesDijk
    Oct 19, 2011 at 6:41

Not sure if you intentionally used the term state chart. State diagrams are more known ( see discussion for comparison )

In the comparison there also is a nice overview of different ways of modelling parallel states in a state chart. I don't know of a real notation of asynchronous state transitions in a state chart but when you model the events and possible states the can happen in parallel you might also show the information that you want. Or you might combine the state chart and state transition diagram.

If you did mean state transition diagram here is a nice overview of different ways of modelling asynchronous state transitions in a state transition diagram

Hope this helps.

  • 1
    -1 This question is not about State transition diagrams :). But seriously could you elaborate a bit about the differences of state charts and uml state diagrams (to my knowledge both hierarchy and paralelism are supported in either. The link you give indicates those 2 as the main difference.
    – refro
    Oct 19, 2011 at 7:20
  • all confused now, your answer is accepted so probably it is about state diagrams, can't take back my minus 1 unless the question is edited. As far as I know the state chart is just a clever/elegant way of showing parallelism. So they both can but the state chart does it more elegant.
    – KeesDijk
    Oct 19, 2011 at 8:03
  • @KeesDijk I am sorry for my vague wording. I don't have solid academic foundation on this topic, and I was just looking for any nice way of visual representation of state transition for concurrent stuffs.
    – Eonil
    Jul 9, 2014 at 20:17
  • The diagram link was broken and I've found it here: web.archive.org/web/20180712154232/http://www.sts.tu-harburg.de/…
    – natenho
    Oct 2, 2020 at 16:10

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