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From "Johannes Wienke (JIRA)" <j...@apache.org>
Subject [jira] [Created] (SCXML-206) Specification mismatch: event-less transitions are triggered by named events
Date Fri, 29 Aug 2014 09:16:54 GMT
Johannes Wienke created SCXML-206:
-------------------------------------

             Summary: Specification mismatch: event-less transitions are triggered by named
events
                 Key: SCXML-206
                 URL: https://issues.apache.org/jira/browse/SCXML-206
             Project: Commons SCXML
          Issue Type: Bug
    Affects Versions: 2.0
            Reporter: Johannes Wienke


The SCXML 2 specification indicates the following in section 3.13

{quote}
A transition is enabled by NULL in atomic state S if a) T lacks an 'event' attribute b) T's
source state is S or an ancestor of S c) T lacks an 'cond' attribute or its 'cond' attribute
evaluates to "true". (Note that such a transition can never be enabled by any named event.)
{quote}

The last aspect that event-less conditions can never be triggered by a named event is currently
violated by the trunk implementation.

Imagine the following example document:
{code:xml}
<scxml xmlns="http://www.w3.org/2005/07/scxml" xmlns:rsb="http://opensource.cit-ec.de/rsb"
	version="1.0" initial="Start" name="CustomActionSequential">
	<state id="Start">
		<onentry>
			<log expr="'Starting onentry of state Start'"></log>
			<send event="'test'" delay="'100ms'"></send>
			<rsb:generic rsb:class="rsb.scxml.LongRunningAction"
				name="first"></rsb:generic>
			<log expr="'Finished onentry of state Start'"></log>
		</onentry>
		<onexit>
			<log expr="'onexit of state Start'"></log>
		</onexit>
		<transition target="End">
		</transition>
	</state>
	<final id="End">
		<onentry>
			<log expr="'onentry of state End'"></log>
		</onentry>
	</final>
</scxml>
{code}
The rsb:generic action is simply a custom action that wastes some processing time by sleeping
1 second.

The logging output that you get when executing this is the following:
{noformat}
Aug 29, 2014 11:04:26 AM org.apache.commons.scxml2.model.Log execute
INFO: null: Starting onentry of state Start
Aug 29, 2014 11:04:26 AM org.apache.commons.scxml2.model.Log execute
INFO: null: onexit of state Start
Aug 29, 2014 11:04:26 AM org.apache.commons.scxml2.model.Log execute
INFO: null: onentry of state End
Aug 29, 2014 11:04:27 AM org.apache.commons.scxml2.model.Log execute
INFO: null: Finished onentry of state Start
{noformat}
As you can see, the named event raised by the send action has triggered the transition since
the outputs are not in the expected sequential order. This should not happen according to
the specification.

On the other hand, if you do not send an event at all, the state machine gets stuck. This
confirms that the transition was actually really triggered by the sent event. Moreover, it
also sounds like a specification mismatch to me. The respective quote from the specification
is:
{quote}
After checking the state configuration, the Processor must select the optimal transition set
enabled by NULL in the current configuration. If the set is not empty, it must execute it
as a microstep.
{quote}



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