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From "Ate Douma (JIRA)" <j...@apache.org>
Subject [jira] [Created] (SCXML-203) Calculation of states to be entered can be depending on states to be exited and thereby also their possible history
Date Mon, 21 Apr 2014 19:32:15 GMT
Ate Douma created SCXML-203:
-------------------------------

             Summary: Calculation of states to be entered can be depending on states to be
exited and thereby also their possible history
                 Key: SCXML-203
                 URL: https://issues.apache.org/jira/browse/SCXML-203
             Project: Commons SCXML
          Issue Type: Bug
    Affects Versions: 2.0
            Reporter: Ate Douma
            Assignee: Ate Douma
            Priority: Minor
             Fix For: 2.0


Currently the SCXMLSemantics implementation calculates the states to be exited and entered
upfront, before the actual exiting and entering is performed.
This is done explicitly to be able to ensure the resulting active states configuration is
a valid one.

However, the currently implementation overlooks the fact that for certain transitions the
states exited may have to be re-entered again. And if for those exited state(s) history is
recorded, then this might influence and change the resulting set of entered states.

Thus the current implementation therefore needs to be corrected for this.

However, following the exact order of processing and execution as defined by SCXML specification
its algorithm for SCXML processing will result in exiting states before the determination
of the states to be entered. The resulting active state configuration is 'assumed' to be always
valid thereafter. 
 
To be able to still ensure the resulting active state configuration to be valid *before* actually
transition to it (like we do now), the calculation of the states to exit will now be done
by also upfront recording the histories for these states (if applicable) as temporary configurations
in the Step itself.
When the step to be taken is ensured to be valid, these 'pre-recorded' histories will be persisted
to the SCInstance when the states are actually exited, while they already can be used before
to determine the proper and correct states to enter if needed.  



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