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Re: Bug with deep and shallow history in pseudo-code

From: chris nuernberger <cnuernber@gmail.com>
Date: Sat, 9 Feb 2013 15:46:18 -0700
Message-ID: <CAG=GWvdwhHMRJcaA+0CjpvfwLdOCuk+uk+nBZ9No_Xk6UPVTBg@mail.gmail.com>
To: Jim Barnett <Jim.Barnett@genesyslab.com>
Cc: Stefan Radomski <radomski@tk.informatik.tu-darmstadt.de>, "www-voice@w3.org (www-voice@w3.org)" <www-voice@w3.org>
getChildStates would not return a history state, would it?

Chris


On Sat, Feb 9, 2013 at 3:22 PM, Jim Barnett <Jim.Barnett@genesyslab.com>wrote:

> Stefan,
>   This clause in enterStates is supposed to catch that case:
>
>                     statesToEnter.add(anc)
>                     if isParallelState(anc):
>                         for child in getChildStates(anc):
>                             if not statesToEnter.some(lambda s:
> isDescendant(s,child)):
>
> addStatesToEnter(child,statesToEnter,statesForDefaultEntry)
>
> but it may be missing something.  I need to look at enterStates and
> addStatesToEnter more closely.  At the very least, they need to be
> reorganized for clarity.
>
> = Jim
>
> -----Original Message-----
> From: Stefan Radomski [mailto:radomski@tk.informatik.tu-darmstadt.de]
> Sent: Saturday, February 09, 2013 1:04 PM
> To: www-voice@w3.org (www-voice@w3.org)
> Subject: Bug with deep and shallow history in pseudo-code
>
> Hi again,
>
> the SCXML document at [1] will put my interpreter in an illegal state
> configuration. I am sure that there is a more concise example that would
> accomplish the same, but it is part of Jacob's test framework.
>
> Initial:
>   Enabled transitions: {root -> a}
>   Stable initial configuration: {a}
>
> t1 arrives:
>   Enabled transitions: {a -> p}
>   Stable configuration: {p, b, b1, b1.1, c, c1, c1.1}
>
> t2 arrives:
>   Enabled transitions: {b1.1 -> b1.2, c1.1 -> c1.2}
>   Stable configuration: {p, b, b1, c, c1, b1.2, c1.2}
>
> t3 arrives:
>   Enabled transitions: {b1.2 -> b2, c1.2 -> c2}
>   Stable configuration: {p, b, c, b2, b2.1, c2, c2.1}
>
> t4 arrives:
>   Enabled transitions: {b2.1 -> b2.2, c2.1 -> c2.2}
>   Stable configuration: {p, b, c, b2, c2, b2.2, c2.2}
>
> When t5 arrives, we exit everything and enter "a" again, thus we have to
> save three histories:
>   hp: {b2.2, c2.2}
>   hb: {b2.2}
>   hc: {c2}
>   Stable configuration: {a}
>
> t6 will transition into "p" again and bring the interpreter into an
> illegal configuration:
>   addStatesToEnter will realize that "p" is parallel an attempt to enter
> all its children
>     Entering hp will enter {b2.2, c2.2} as its history
>     As "p" is parallel, we will enter "c" as well, as it is compound, we
> will enter its initial shallow history "hc", adding "c2"
>       "c2" is compound and its initial state "c2.1" will be entered.
>
> -> we now have "c2.2" and "c2.1" in the configuration which is illegal.
>
> Who is supposed to prevent "c2" from entering its initial state? We
> already entered "c2.2" per deep history from "hp" and now the shallow
> history from "hc" wants to enter "c2" and ultimately its initial state
> "c2.1" leading to an invalid configuration.
>
> Best regards
> Stefan
>
> [1]
> https://github.com/jbeard4/scxml-test-framework/blob/master/test/history/history4.scxml
>
>
>
>
>
>


-- 
A foolish consistency is the hobgoblin of little minds - Emerson
Received on Saturday, 9 February 2013 22:46:45 GMT

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