RE: [scxml] semantics of nested history in parallel state ISSUE-773

Johan,

Yes, I can see that the algorithm would have this problem  (it wouldn’t if the transition were labeled ‘internal’).  An additional problem is that we don’t define getProperAncestors(state, ancestor) anywhere.  If it is defined as not including ‘ancestor’ in its returned values, this problem definitely occurs (because in this case ‘ancestor’ is parallel state ‘p’).  If the return value does include ‘ancestor’ (‘p’ in this case) then I think that this case will work, but other things may be broken.

 

-          Jim

 

From: www-voice-request@w3.org [mailto:www-voice-request@w3.org] On Behalf Of Johan Roxendal
Sent: Monday, June 27, 2011 11:59 AM
To: www-voice@w3.org
Subject: RE: [scxml] semantics of nested history in parallel state

 

Hey,

 

So Torbjörn sent me the upcoming algorithm, which I transcribed into PySCXML. There seems to be a problem, I'm afraid (as PySCXML user DairTarg pointed out in the issue tracker):

 

<scxml version="1.0"

            xmlns="http://www.w3.org/2005/07/scxml" initial="p">

 

    <parallel id="p">

        <state id="s" initial="a">

            <state id="a" />

            <state id="b" />

            <transition event="e" target="b" />

        </state>

        <state id="s2" />

    </parallel>

</scxml>

 

The above machine starts out by going to the configuration {p, s, a, s2}, which seems correct. however, when sent the event 'e', it reacts by leaving s and s2 (correctly) and entering s and b (correctly) but not s2. thus we find ourselves in the illegal configuration {p, s, b}. so, that's not good. 

 

i've tested the same example with the version of the algorithm that used recursivelyAddDefaultDescendants, but same result there. It could still, of course, be the result of a transcription error (i've gone over the transcription several times, but it's hard to be sure).

 

regards,

johan


     
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