On Mon, Feb 15, 2016 at 12:17 PM, Vicente J. Botet Escriba < vicente.botet@wanadoo.fr> wrote:
Le 15/02/2016 11:08, Krzysztof Jusiak a écrit :
On Fri, Feb 12, 2016 at 6:44 PM, Vicente J. Botet Escriba < vicente.botet@wanadoo.fr> wrote:
Le 12/02/2016 12:20, Krzysztof Jusiak a écrit :
For me it is semi clear, but I do agree with your conclusion though. However, there is no info about guards being executed before src state exit. It might be implied by the statement that transition has to be enabled, but I'm not sure about it.
Yes, I believe that event reception and the guard evaluation are the enablers of the transition.
Yea, but that would mean that guard has to be evaluated before exit of the state or any action, so the order would be. 1. guard [to enable transition] 2. exit src state 3. actions... 4. entry dst state When the actual state change should happen in above sequence it's not stated in the document as well. I would assume following order according to the spec + a bit of rationality? 1. guard [to enable transition] 2. exit src state 3. actions... 4. CHANGE THE STATE TO DST HERE? 5. entry dst state
BTW. I have a question related to local transitions. Concept seems to be
nice but I don't undesrtand why exit/entry is NOT triggered only 'if the
main target state is a substate of the main source'. Why this concept can't be more general? Wouldn't that be nice?
s1 + e1 = s2 // exit from s1 / entry to s2 s1 ^ e1 = s2 // no exit from s1 / no entry to s2
A local transition will ensure that there is no exit on s1, but there
should be an entry in s2 if s2 is not s1. You will need to have a nested examples to see the difference between an external and a local transition.
Yea, I do get it. Cheers. Do have any example when local transitions are useful? I see some usage for them but I struggle really to find a really good use case for them.
Let say that you have a state S with two sub-states S1 and S2.
While in state S, if you receive the event E1 you want to go to S1, but don't want to execute the exit of state S. However you want to execute the exit of S1 or S2.
S ^ E1 = S1;
Think of E1 as an event that interrupts whatever you were doing on S1 or S2.
Yea, yea I do get that. I was asking more about real life example. I mean, what use case would require such behavior, because I can't think of any, but I know there are some. I'm asking because I don't have any experience with local transition and it is hard to justify adding a new feature without a meaningful rationale.
Let say that we are on a disabled state. In this state you have sub-states representing the path to go to another enabled state (e.g. requesting a password, ...) . If you receive a reset event this would disable any trial to go to the enabled state. From the disabled state you could have a local transition when receiving this reset event and go to the sub-state disabled/idle. What is important is that you are always in the disabled state, so the disabled exit has not been executed.
Cheers, it helps a lot.
Vicente
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