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RE: [SCXML] <anchor> stuff?

From: Serge Voloshenyuk <serge_voloshenyuk@yahoo.com>
Date: Mon, 16 Apr 2007 13:20:50 -0700 (PDT)
To: www-voice@w3.org
Message-ID: <427026.40124.qm@web34308.mail.mud.yahoo.com>
Thanks for your prompt answer.

>Question 1:  <anchor> transitions can be chained.  Suppose states S1 and
>S2 both have <anchor>s of type "Foo" and the machine enters S1, then S2,
>then S3.  If the machine then takes a transition with 'anchor' "foo", it
>will return to S2 and roll back the data model.

And in this point machine enters to state S2 with anchor "Foo"
and saves state S2 as last visited for anchor type "Foo".
So in next transition to anchor "Foo" it must go to state S2.

I do understand your explanation but in this case you have to describe in the next draft that
memory for saving anchor visits must be stack and this stack will be changed only in regular visit 
but not in case of rollback by <anchor> transitions. 

"Question 2:  When the machine takes a transition with 'anchor' of "Foo"
back to state S2, the snapshots of all anchors visited since the last
time we were in S2 are erased (i.e. all snapshots "between" S2 and the
state that is the source of the transition.)"

All - is it meant other anchor types too?

"Given the logic of
anchors, none of these states can have an <anchor> of type "foo"."

So, as I understood I have to have sole stack of visited anchored states and 
in rollback must pop states from this stack (with clearing all related snapshots)
until find state with destination anchor.
Is it true?

"Question 3:  The current draft is not clear on this.  I would say it is
the state containing the <transition> with the 'anchor' attribute."

Yes, this looks as most reasonable case.
But I would like to note that placement transition to some level of state hierarchy
can have just a reason of avoidance of repetitions in child states.
I can't imagine the rollback transition from leaf state 
and especially sense for reentering to this state.

But in the end I fell that I have more questions than I had. 
Could you publish some primer for this feature?
The primer that you have in mind when you invented anchors.

Regards, Serge.

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Received on Monday, 16 April 2007 20:20:58 UTC

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