Le 12/02/2016 12:20, Krzysztof Jusiak a écrit :
On Thu, Feb 11, 2016 at 12:28 PM, Vicente J. Botet Escriba < vicente.botet@wanadoo.fr> wrote:
It seems that we need to inspect the UML2.1 documentation to check what is the specified behavior. If it is undefined, the argument in MSM would be valid.
I checked UML2.5 specification and I have found "Transition execution sequence" (14.2.3.9.6 / page 316). However, there is no much info about the sequence there. It's mostly about that exit of the main state has to happen before entry to the target state. I can't find anything about when guard/action should happen in the sequence :/ buy it's a long document so maybe it might be found somewhere?
On page 377 I see an example where the order is clear xS11; t1; xS1; t2; eT1; eT11; t3; eT111 Where xAAA means exit action on state AAA and eAAA entry on state AAA. ti are actions on the segmented transitions. Just before this example you can find *"Transition execution sequence ** *Every Transition, except for internal and local Transitions, causes exiting of a source State, and entering of the target State. These two States, which may be composite, are designated as the main source and the main target of a Transition respectively. The main source is a direct substate of the Region that contains the source States, and the main target is the substate of the Region that contains the target States. NOTE. A Transition from one Region to another in the same immediate enclosing composite State is not allowed. Once a Transition is enabled and is selected to fire, the following steps are carried out in order: 1. Starting with the main source State, the States that contain the main source State are exited according to the rules of State exit (or, composite State exit if the main source State is nested) as described earlier. 2. The series of State exits continues until the first Region that contains, directly or indirectly, both the main source and main target states is reached. The Region that contains both the main source and main target states is called their least common ancestor. At that point, the effect Behavior of the Transition that connects the sub-configuration of source States to the sub-configuration of target States is executed. (A “sub-configuration” here refers to that subset of a full state configuration contained within the least common ancestor Region.) 3. The configuration of States containing the main target State is entered, starting with the outermost State in the least common ancestor Region that contains the main target State. The execution of Behaviors follows the rules of State entry (or composite State entry) described earlier. " I believe this is clear enough. 1 exits 2 action 3 entries
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. Vicente